Ranking Red Sox's Best Closer Candidates If Aroldis Chapman Is Traded

[Ben Lofy]

With the trade deadline just about six weeks away, it is widely expected that the Boston Red Sox will look to trade away Aroldis Chapman.  One of the game’s greatest closers in recent history, Chapman is in his age-38 season and playing for his seventh team. Despite being in the twilight of his career, Chapman has found success in Boston unlike anywhere else. 

Across 61.1 innings in the 2025 season Chapman posted a 1.17 ERA, the second-lowest mark over his 17-year career and the lowest since 2016. His success has carried over into 2026, as he is one of the lone bright spots of the Red Sox's underwhelming season thus far. Through 21.2 innings, the lefty has tallied an ERA of 0.83 and a 0.97 WHIP. 

His stellar stats amid a season of team disappointment make Chapman a clear trade chip. Should the Red Sox look to the future, there are a few candidates to take over the ninth inning in Chapman’s absence.

Ranking Red Sox's 4 Best Replacement Plans for Aroldis Chapman

We'll go in order here, with the best (and most likely) candidate first followed by a trio of less-heralded options.

Garrett Whitlock

Whitlock has blossomed into one of the league's most reliable set-up men over the past few seasons. The Rule-5 draft pick from the New York Yankees made an immediate impact in Boston, turning in a sub-2.00 ERA over 73.1 innings in his first big-league season. After missing the majority of the 2024 season with injury, Whitlock bounced back strongly in 2025. He pitched in a career high 62 games to the tune of a 2.25 ERA and 91 strikeouts, another career high. 

Through the start of the 2026 season Whitlock has played the same set-up role as last season, and he’s played it well. Through 21.2 innings, Whitlock has produced a 2.91 ERA and four wins. Inarguably one of Boston’s most consistent and reliable bullpen pieces this decade, Whitlock seems to be the heir apparent to the closer role. It makes too much sense to give Whitlock the extra responsibility. He has consistently proved his ability to perform under pressure and has long been one of the league's premier late-inning relievers. 

Tommy Kahnle

Should the Red Sox desire to leave Whitlock in his current role, the next logical closer option would be Tommy Kahnle. A 12-year MLB veteran, Kahnle signed a minor-league deal with the Red Sox late in the offseason and began his 2026 campaign in Triple-A Worcester. In early June. Kahnle triggered an upward mobility clause, forcing the Red Sox to add him to the roster, lest he would opt-out and seek other opportunities. He impressed upon arrival, tossing four consecutive scoreless appearances (though he's allowed three runs over his last two innings).

Despite the small big-league sample size in 2026, Kahnle’s career 3.58 ERA and his track record of success in the majors make a convincing argument for him to take over as the teams closer. Just two years ago, Kahnle posted a 2.11 ERA as a member of the Yankees. His changeup played a big role in his success, holding batters to a .157 average and generating a 38.9% whiff rate. He used the pitch 73% of the time and has similarly leaned into his changeup in 2026. While his smaller 2026 sample size doesn’t display astounding results, it isn’t a far-fetched possibility that Kahnle with his 17 career saves could be a reliable option for the remainder of the season. 

Tyron Guerrero

Another player recently promoted from Triple-A, Guerrero is a power throwing righty. However, his career path has been less than conventional. The 35-year-old has played in parts of four seasons dating all the way back to 2016 and found a consistent role with the Miami Marlins from 2018-2019 but saw undesirable results. Guerrero bounced around the minors and overseas leagues before landing in Worcester this past January. He settled into a closing role with the WooSox, posting a 0.92 ERA across 19.2 innings pitched and earning a call up to Boston in late May.  

Guerrero has a four-pitch mix but relies heavily on his sinker, utilizing it 76% of the time. His fastball velocity is in the 99th percentile according to Baseball Savant and he averages 99.9 MPH on his sinker. Guerrero clearly has the tools to be an effective closer, but it all comes down to application. He gave up four runs through his first three big league appearances in 2026, good for a 9.82 ERA. However, in eight outings since then, Guerrero has only allowed one run, settling into a 4.35 ERA. Given his recent reliability, the veteran could be the most logical option to take over the closer role if Whitlock stays in his set-up role and Kahnle follows Chapman out the door at the trade deadline. Additionally, Guerrero has seen success as a closer in Worcester and has proven that he can be trusted to take over in high-stakes situations. 

Eduardo Rivera

If Boston decides to look fully to the future, Eduardo Rivera is an intriguing name who could see more playing time as the season continues to slip away. A well-regarded pitching prospect, he got attention earlier this season when he was promoted to the big-league club without making a single appearance in Triple-A. In one relief appearance in Boston, he dominated. Over 3⅓ innings against the Yankees, Rivera allowed just one hit as he struck out three batters. In the two months since then, he has accumulated a 3.29 ERA while holding opponents to a .188 batting average, albeit entirely in the minors. While Rivera isn’t a traditional closer and typically fills in a multi-inning role, his ability to perform well under pressure helps make a case for a potential role change. Additionally, if the season continues to unravel, the experience of high-leverage work could be beneficial for Rivera’s development down the line.

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