September baseball is here. Rosters expanded to 28 players on Tuesday as teams look to make a final push towards a division title or squeeze into a wild card spot. Teams in contention will hope the two spots can provide juice to their bench or pitching staff down the stretch. Such is the case with the Boston Red Sox, who called up pitcher Zack Kelly and reacquired catcher Ali Sanchez from the Mets. Despite the call ups, there are players left in Boston’s minor league system who are able if not likely to help them on their run to October baseball.
Here are three minor league players who could contribute for Boston in September:
Kyle Harrison
A substantial piece of Boston’s return in the controversial Rafael Devers trade in June, Harrison was immediately optioned to Triple-A Worcester upon his arrival. While many fans were disappointed by the demotion, mostly due to the circumstances he was acquired under, it seems the decision could turn out fruitful for Harrison’s future. Part of getting back on track for Harrison has been making adjustments to his arsenal.
Harrison’s best pitch has long been his fastball, which has received grades between 60-70 from major prospect publications since at least 2021. The righty relied on that pitch during his first extended look in the majors in 2024, throwing the pitch 57.6 percent of the time. That usage skyrocketed over eight MLB games in 2025, as he threw the pitch 65.2 percent of the time. While there was an uptick in velocity on the pitch — almost three miles per hour on average compared to 2024 — Harrison essentially turned into a one pitch pitcher as opposing batters crushed his slurve and changeup for averages of .381 and .286, respectively. Since arriving in Worcester, Boston has completely revamped the former top 100 prospect’s pitch usage. Harrison barely used his slider, which has long graded as his second-best pitch, at the MLB level in 2024 and not at all in 2025. With Worcester, the 6-foot-2 starter is now throwing a slider 18.3 percent of the time while reducing his fastball usage to 50.9 percent. If the California native can utilize that pitch mix to generate higher strikeouts rates, as he did in the past in San Francisco’s organization, he could still turn out to be a two or three starter in the MLB. Harrison was passed up for a major league promotion due to the unexpected emergence of pitcher Payton Tolle. Still, the 24-year-old has time to make good on his potential and should be the next pitcher up if Boston needs a starter in September.
Chris Murphy
Murphy has already shown that he can be productive on a big-league mound and be valuable to a contending bullpen. Murphy began 2025 on the injured list recovering from April 2024 Tommy John surgery. Following a month-long rehab assignment, he joined the Red Sox bullpen immediately upon his activation. The lefty made 14 appearances, giving Boston 20.2 innings of work to a 3.05 ERA and striking out almost a batter per inning. The multi-inning option allowed an earned run in only four of his 14 games and gave the team six appearances of over one inning. Despite that success, Murphy was optioned to Worcester in mid-July to allow the Red Sox to select a fresh arm in Jovani Morán. In 12 games for Worcester, including two starts, the 27-year-old has maintained his strong strikeout numbers while posting a 1.69 ERA for the month of August. Despite being passed over for Kelly in Boston’s initial September call ups, Murphy seems likely to get back to Boston before the end of the season as they look to keep their bullpen fresh down the stretch.
Kristian Campbell
Campbell is a name that Boston fans are likely familiar with. A member of Boston’s “Big Three” prospects (also including outfielder Roman Anthony and infielder Marcelo Mayer), Campbell signed an eight-year, $60 million dollar pre-debut contract extension with two additional club options prior to the 2024 season, according to Jeff Passan. The Georgia Tech alum made the Red Sox Opening Day roster and started as Boston’s second baseman. Campbell became the first member of the “Big Three” to make his debut, and that decision was paying off for Boston in the season’s first month.
After putting up an .848 OPS in the month of April and winning AL Rookie of the Month, the 23-year-old’s numbers took a nosedive in May and June. Questions about Campbell’s defense at second base also came up as he committed seven errors in just 59 games. The struggles even led to Campbell taking reps at first base amidst the Rafael Devers saga. Campbell was optioned to Triple A on June 20.
Anthony and Mayer have both debuted, leaving Campbell as the only member of the “Big Three” left in Triple A. With Worcester, Campbell has righted the ship offensively. The right-handed-hitter hasn’t reached the peaks he showed last year or even early in 2024, but he has been a consistent offensive contributor for over two months with the Woo Sox. Defensively, Campbell has turned into something of a utilityman with Worcester. A plus athlete, he has seen time in both left and center field in addition to first and second base.
Given his extension, it’s unlikely that the Red Sox will give up on Campbell any time soon. While the rookie has been jumped by multiple, less-heralded players for call ups to Boston, he remains Boston’s highest upside depth option and seems likely to eventually be given a second chance at the major league level before September is up.