Every player always has something to prove, but some have quite a lot on the line.
With the end of the regular season on Sept. 28 in sight, many players are under considerable pressure. Some must lead the charge in propelling their teams to the postseason, while others are simply trying to end personal down years on a positive note. And there are quite a few young players looking to find — or maintain — early-career success in the big leagues.
Who has the most at stake as September gets into full swing? With the help of MLB.com’s 30 beat writers, here’s one player on each team with the most to prove down the stretch in 2025.
Blue Jays: OF Anthony Santander
Toronto’s biggest offseason splash on a five-year, $92.5 million deal, Santander hasn’t been seen since late May, and his first two months weren’t pretty. There’s finally a plan in place for Santander to take a run at returning down the stretch, though, and what a story that would be in a season where it feels like (almost) everything has gone right for the Blue Jays. Fans in Toronto know what Santander is capable of from his time with Baltimore, but there’s no better time to give them their first taste of what that looks like in a Blue Jays uniform. — Keegan Matheson
Orioles: 1B Coby Mayo
Can Mayo serve as Baltimore’s starting first baseman in 2026? The 23-year-old former top prospect has another month to state his case. Mayo has shown a lot of defensive improvement this year at first, which was his secondary position when he was a Minor League third baseman. But Mayo still needs to prove he can hit in the big leagues — he has mostly struggled, hitting .188 with a .596 OPS in 63 games this year entering Wednesday. Ryan Mountcastle is under team control again in 2026, while Samuel Basallo has arrived, so the O’s will have options at first. — Jake Rill
Rays: SS Carson Williams
With Ha-Seong Kim claimed off waivers by the Braves and Taylor Walls still on the injured list, the shortstop job belongs to the Rays’ top prospect the rest of this month. That gives the slick-fielding, power-hitting rookie a chance to lock down the job for next season as well, or at least to learn about what it will take for him to produce at the Major League level heading into the offseason. This season didn’t go the way the Rays wanted, but they can make the most of this month by getting Williams acclimated in the infield. — Brian Murphy
Red Sox: DH/OF Masataka Yoshida
Yoshida has had an uneven first three years in the Major Leagues. In his rookie year, he thrived until hitting a wall the last two months of the season. Last season, he battled injuries and missed time but had some hot streaks mixed in. In 2025, he quite simply hasn’t been able to get much going at the plate since his activation just prior to the All-Star break. If Yoshida is going to be part of manager Alex Cora’s playing mix down the stretch and into October, he needs to start producing. — Ian Browne
Yankees: SS Anthony Volpe
Volpe heard boos on the Yankees’ most recent homestand, and his turbulent campaign earned him consecutive days out of the lineup, the first time in his three Major League seasons that has occurred. The span served as both a physical and mental reset for Volpe, who hit .172 in July and .191 in August. Volpe’s defensive issues have also been a concern; he leads the AL with 18 errors, though the Yanks remain steadfastly in his corner as their starting shortstop. — Bryan Hoch
Guardians: RHP Tanner Bibee
Bibee could use a strong finish to what has been an up-and-down 2025. The right-hander (who was Cleveland’s ace in 2024) has recorded a 4.77 ERA in 154 2/3 innings over 27 starts and has been working relentlessly to get on track. Bibee’s underlying metrics indicate some tough luck; his expected ERA is 3.82, and his hard-hit rate is 37.6 percent (76th percentile). His strikeout rate (20.6%) has gone down since last year (26.3%), and his homers per nine innings (1.51) are up from 1.14 in 2024. — Tim Stebbins
Royals: RHP Seth Lugo
Kansas City’s most reliable starting pitcher since the start of last season has been anything but of late, and the Royals need him to return to form if they are going to make a serious postseason push. Lugo’s ERA has ballooned to 4.15 — from a season-low 2.65 on July 3 — after he allowed four or more runs in four of his past five outings. The Royals signed him to a two-year, $46 million extension in July to be their workhorse, and they need him to pitch like he did in June (1.26 ERA) if they are going to challenge for an AL Wild Card spot. — Jackson Stone
Tigers: RHP Jack Flaherty
Flaherty’s return to Detroit on a two-year, $35 million deal has been a mixed bag. The righty has been downright unhittable at times — fanning nine over seven scoreless frames against Houston on Aug. 18 — but has also taken his fair share of lumps (see: two 8-ER starts and one of 7). The Tigers’ rotation is largely in flux behind Tarik Skubal, and Flaherty finding his groove down the stretch would be a huge boost. — Dawn Klemish
Twins: SS Brooks Lee
It’s been a summer of turnover in the Twin Cities, so there are plenty of candidates, rookies and veterans alike. But for Lee, it’s a huge stretch. He’s been installed as the everyday shortstop for the final two months, and he’s held his own so far. If he can handle the position and produce offensively, he could convince the Twins that they don’t need to find a shortstop this winter. — Matthew Leach
White Sox: SS Colson Montgomery
Montgomery has homered in consecutive games six times this season, and the 16 home runs through his first 47 career games are second most by a White Sox player to start a career behind only José Abreu (17) during his 2014 AL Rookie of the Year campaign. So what does Montgomery possibly have to prove over the final month? He needs to continue playing solid defense at shortstop and claiming the position, which he has done since arriving with the White Sox on July 4, and show his overall growth and development as a hitter beyond the immense power. Montgomery’s big-league emergence has been the top White Sox rebuild story in 2025, helping the overall outlook going into 2026. — Scott Merkin
Angels: INF Oswald Peraza
The Angels acquired Peraza, a versatile infielder, from the Yankees at the Trade Deadline. Since then, he’s slashed just .226/.250/.355 in 16 games, entering Wednesday. The Angels’ current primary third basemen — Yoán Moncada and Luis Rengifo — are both upcoming free agents. With Peraza under contract through 2029 and out of Minor League options, he has a chance to make his case to start next season if he can turn it around in September. — Andrés Soto
Astros: OF/DH Yordan Alvarez
Alvarez missed 100 games with a fractured hand, returning to the lineup Aug. 26. He was 6-for-18 with a homer in his first seven games back, walking eight times (.519 on-base percentage). Alvarez had a pair of massive home runs in helping the Astros win the World Series in 2022, and Houston’s hit-or-miss offense needs the slugger to provide a power stroke. — Brian McTaggart
Athletics: OF Lawrence Butler
Butler’s dynamic abilities have been on display as he closes in on becoming the first A’s player with 20 homers and 20 stolen bases in a season since Coco Crisp in 2013. Entering Wednesday batting just .230 with a .709 OPS, however, is probably not where the A’s expected him to be in September after signing him to a five-year extension this offseason. Consistency at the plate will be key for Butler over this final stretch. — Martín Gallegos
Mariners: RHP Luis Castillo
Once a total embodiment of his nickname, “The Rock,” Castillo has been far from it over the past month-plus, with a 7.31 ERA since Aug. 1, over which opponents have hit nine homers and tagged him for a 1.041 OPS. The Mariners, who have been unable to chase down Houston in the AL West since the Trade Deadline, have gone 2-4 in those outings. Castillo is also their most expensive player, and his no-trade clause expires this winter, which could lead to longer-term questions about his future in Seattle. But at least for now, they need him to figure out his issues over what could be a defining stretch in September. — Daniel Kramer
Rangers: RHP Jacob deGrom
Performance wise, deGrom has never needed to prove anything to anybody. But he’s a guy that hasn’t seen a full healthy season of baseball since 2019. deGrom has stated many times that making 25-30 starts in his first year removed from his second Tommy John surgery was a stated goal. So far, he’s one of the only members of the Rangers rotation to avoid the injured list. He’s made 26 starts and has totaled 150 1/3 innings. Finishing out the season strong and healthy would do wonders for the general perception of deGrom’s sturdiness. — Kennedi Landry
Braves: SS Ha-Seong Kim
With Kim holding a $16 million option for 2026, the Braves might actually be the portion of this relationship with the most to prove. If Kim can distance himself from recent injuries and find comfort with Atlanta, the former Gold Glover’s stint with the Braves could extend beyond this season’s final month. By claiming Kim off waivers from the Rays on Monday, the Braves already showed their hope Kim erases the need to find a shortstop this winter. — Mark Bowman
Marlins: C Agustín Ramírez
When Miami acquired Ramírez – then a top prospect – in the Jazz Chisholm Jr. trade last summer, the organization did so with the belief that he could catch at the big league level. Entering Monday, the 23-year-old rookie led MLB backstops (min. 450 innings) in errors (nine) and passed balls (15) and was tied for the second-fewest Defensive Runs Saved (-11). Ramírez must show progress to assure the Marlins he can remain behind the dish. — Christina De Nicola
Mets: RHP Kodai Senga
With rookies Nolan McLean and Jonah Tong making their mark on the pitching staff, the Mets don’t have tons of room in a potential playoff rotation. That could directly affect Senga, who must prove more trustworthy if he wishes to be part of the team’s October plans. The Mets don’t necessarily need Senga to pitch deep into games, but they do need him to cut down on walks and provide better results overall. He hasn’t done that consistently since the first half of the season. — Anthony DiComo
Nationals: LHP Mitchell Parker
Parker went 0-4 with a 12.00 ERA while struggling to pitch deep into games in his first five starts in August. The Nationals kept him in the rotation, and he concluded the month with a turnaround 6 1/3-inning outing against the Rays. Parker will look to keep that momentum and end his second Major League season on a high note before the Nationals evaluate their 2026 starting rotation this winter. — Jessica Camerato
Phillies: RHP Aaron Nola
Nola has not only established himself as a fixture within the Phillies’ rotation over the past decade, but he’s also been one of the most consistent starters in the Majors during that time. But after missing three months this season due to a sprained ankle and a stress fracture in one of his ribs — his first non-COVID-related IL stint since 2017 — Nola is still looking to find his footing in 2025. The Phillies need him to step up now more than ever after losing ace Zack Wheeler for the rest of the season. — Paul Casella
Brewers: RHP Jacob Misiorowski
Ever since Misiorowski took MLB by storm in June and early July, including a history-making appearance in the All-Star Game, nothing has come easy for the 23-year-old. There was a planned break in July, then an unscheduled break in early August when a comebacker off the right shin sent Misiorowski to the injured list. In six starts since the break, he has a 6.45 ERA and has not pitched beyond the fifth inning. Still, the Brewers plan to use Misiorowski as a starter — “We need him as a starter right now,” manager Pat Murphy said — and hope to get him on track in time to be a weapon in a postseason rotation with Freddy Peralta and Quinn Priester. If that doesn’t happen, the Brewers may have to think about whether he’s more valuable this fall in relief. — Adam McCalvy
Cardinals: OF Jordan Walker
The Cardinals have made it abundantly clear that they want to see a strong finish to the season from Walker, who has struggled at the big league level for a third straight year. Walker, 23, showed some promise after the All-Star break, hitting .304 with six doubles, four RBIs and an .808 OPS in July. However, Walker’s struggles returned in August when he struck out 25 times compared to walking just four times. He went into Wednesday with 10 strikeouts in his previous six games. Cardinals manager Oliver Marmol said on Tuesday that Walker needs to be more receptive to making changes and must show more of a “sense of urgency.” — John Denton
Cubs: OF Kyle Tucker
While Tucker has seen a recent uptick in production, his uncharacteristic slump through July (.675 OPS) and August (.735) played a big role in the Cubs’ overall offensive decline in that span. When Tucker was hitting at an MVP-caliber level early on, Chicago was rolling out one of baseball’s most potent lineups. The Cubs need Tucker (who left Tuesday’s game with left calf tightness) firing on all cylinders down the stretch, especially if the team hopes to have a deep October run. Tucker’s finish to this season will also impact the size of the contract he’ll then be able to pursue in free agency. — Jordan Bastian
Pirates: SS Jared Triolo
Triolo had an outstanding month of August, slashing .315/.417/.467 over 109 plate appearances, good for 1.2 fWAR. Considering how he was playing before being optioned to the Minors in July (.519 OPS, -0.2 fWAR), it was sorely needed. With Ke’Bryan Hayes and Isiah Kiner-Falefa gone, there are opportunities on the left side of the infield for next year. Another strong month would help make a case that Triolo should be the everyday guy at one of those two spots. — Alex Stumpf
Reds: 2B Matt McLain
After missing all of 2024 with a shoulder injury on the heels of a very nice rookie season, McLain has had a rough offensive year. Despite 13 homers, including two over the weekend, he has yet to find a consistent groove, batting .226/.305/.346, despite some steady defense. With top prospect Sal Stewart just called up and able to play second base, McLain will be seeking a strong final month to keep himself in the regular lineup as Cincinnati fights to stay in the playoff race. — Mark Sheldon
D-backs: INF Jordan Lawlar
Lawlar was called up for the third time in his career last week. The first time was in September 2023, and he saw minimal playing time while struggling at the plate. He received his second callup earlier this year and once again did not see consistent playing time and was hitless. This time around, the team wants to make sure he gets plenty of at-bats, and it’s time for Lawlar to show what he can do with them. — Steve Gilbert
Dodgers: OF Michael Conforto
The Dodgers had hoped to unlock something closer to Conforto’s early-career form when they signed him to a one-year, $17 million deal, but that has not materialized. He had a strong July, but it was the only month he’s batted above .200 this season. With Max Muncy, Tommy Edman and Hyeseong Kim on the way back, Conforto could not only be fighting for playing time but also for a spot on the postseason roster. — Sonja Chen
Giants: OF Luis Matos
After trading Mike Yastrzemski to the Royals, the Giants plan to give Matos and fellow youngster Drew Gilbert a chance to get regular at-bats in right field down the stretch. Matos has been making the most of the opportunity thus far, but he’ll need to sustain that production to prove that he should be part of the outfield mix in 2026, when he’ll be out of Minor League options. — Andrés Soto
Padres: RHP Dylan Cease
It’s been a strange year for Cease, who has shown flashes of the dominance that twice landed him in the top five of Cy Young voting — but without any measure of consistency. Throughout the summer, Cease dealt with trade rumors, but San Diego opted to hold onto him amid a frenzied Trade Deadline. If the Padres are going to make an October run, Cease, a pending free agent, is going to need to shake off some of the demons from last postseason. They’ll need him to start (and win) some big games. — AJ Cassavell
Rockies: RHP Antonio Senzatela
Senzatela returned this season after a lengthy rehab from Tommy John surgery, but only rarely this season did he appear to recapture his form. After Senzatela went 4-15 with a 7.42 ERA in 23 starts, manager Warren Schaeffer moved him to the bullpen to work out his issues. Senzatela is signed through next season at $12 million, and the Rockies will be looking for signs that he is finding himself. — Thomas Harding
