Aroldis Chapman is one of the best closers of all time. From 2012 until 2021, Chapman consistently was near the top of the league in saves. His fastballs have always been among the best in terms of sheer velocity, and he is still able to reach 100 MPH with ease. Chapman's best years came in Cincinnati and New York with the Yankees.
The left-handed pitcher has had most of his appearances (1,115 at-bats) in high-leverage situations. In his career, he has allowed a slash line of .167/.283/.266 and has struck out over 45% of batters he's faced in those situations. It would appear that Chapman, as a lefty who can pitch in high-leverage innings, would be a reliever the Cardinals should sign this offseason; however, there are some factors that go against that belief.
Chapman is getting old. He will spend the entire 2024 season at 36 years old. The Cardinals signed Andrew Miller in his age-34 season, and he started showing signs of age quickly; they signed Greg Holland in his age-32 season, and that experiment failed; they also signed Brett Cecil in his age-30 season, and despite his strong 2017 season, he fell off heavily in 2018. Chapman will be 36 next year, and he has been a flamethrower for his career. There is sure to be soreness, injury possibilities, and fatigue in the former closer.
Another concerning factor about Chapman would be his postseason performance this year. In 7.1 innings, he has a 2.45 ERA and 1.50 WHIP, both respectable numbers. His strikeout numbers, however, have dropped compared to his regular season totals. He has only five strikeouts to four walks this postseason. He is also allowing the most hits in the postseason for his career. We could already be seeing fatigue set in for the All-Star closer.
While Chapman is a lefty who has shown an ability to pitch well in high-leverage innings and has been durable, there are some initial cracks showing in his game. Chapman would be a fine addition to the bullpen, but he is getting old, and he has become more erratic as the season and postseason have progressed.