Kenley Jansen Is Putting His Body on the Line for the Red Sox

In case you hadn’t noticed, Kenley Jansen has quietly put up an extremely solid season. His 52.2 innings pitched rank second among Boston relievers. His 3.42 ERA and 3.04 FIP rank second as well. He’s put up 1.4 fWAR, most among Boston’s relievers, and less than a third of a win behind any starter except for Brayan Bello. Those 1.4 WAR also rank 21st among all relievers this season. I’m going to say that again because it bears repeating: 632 pitchers have thrown at least one inning in relief this season, and Jansen has put up more value than 611 of them. The Twins, the Orioles, the Diamondbacks – these are just a couple of the playoff teams that would kill for a reliable pitcher like Jansen right now. However, I don’t get the sense that the Red Sox are particularly concerned right now about whether or not they bring him back next season. I say that not because I have a source or any inside information about the situation. I don’t. I say that simply because they’re not necessarily using him the way a team normally uses a pitcher whose long-term health is a priority. 

Jansen pitched a scoreless ninth inning against the Rays on Wednesday, earning his 27th save of the season in the process. He also injured his shoulder. Jansen quickly retired his first two batters, then grimaced repeatedly while facing the third, prompting a visit from Alex Cora and a trainer after Jansen issued a walk. The visit didn’t last long. Jansen walked another batter, putting the winning run on base, then went to a three-ball count on the next before fighting back for a strikeout to end the game. “He’s been dealing with some shoulder stuff,” Cora said after the game. “I checked with him. He’s like, ‘I’m good, I’m good to go.’” To be clear, this is nothing new.

Jansen pitched through a lat injury earlier this month. On September 6, he told reporters, “I won’t pitch until this [calms] down.” It’s not clear when the injury first reared its head, as he didn’t pitch that day. However, he pitched the next day, which doesn’t really sound like the injury was given much time to calm down. He next pitched in back-to-back games on September 11 and 12. Back-to-backs are particularly tough on a pitcher’s arm. They’re definitely not standard protocol for a pitcher who just put an injury behind them, or, in what was almost certainly Jansen’s case, attempting to pitch through an injury. Perhaps you remember the hubbub from back in May, when Buster Olney reported on the rules that Josh Hader laid down for the Brewers following the 2019 season: “He would not pitch more than two days in a row; he would not pitch more than three outs; he would pitch only in a save situation or when the score was tied.” Some fans didn’t like the idea of a player dictating his own usage to a team, but they kept Hader healthy — not to mention one of the absolute best pitchers in baseball — for the next three years. When Hader reached free agency following the 2023 season, wrote Olney, “Team doctors reviewed his medical records, which sources from multiple front offices described as ‘very unusual’ because they didn't reflect the wear and tear normally seen for a reliever with as many years of service as Hader.”

Just to break down the timeline again, Jansen revealed that he was hurt on September 6 and said that he wouldn’t pitch until the injury improved. Then he pitched the next day. Not at all coincidentally, his velocity also ticked way down. Starting on September 7, his sinker has averaged 91.4 mph, down more than two full ticks from the 93.5 he averaged earlier in the season. Four days later, the Sox had him pitch in back-to-back games. He got five days off after that, but it shouldn’t come as a shock at all that after taking the mound on Wednesday, he left in even worse shape. The injury is now described as affecting both his lat and shoulder, but there isn't much clarity about what exactly is wrong.

Jansen is about to be a free agent, and ending the season on the IL is not a great way to command top dollar on the open market. More importantly, he’s a ferocious competitor who badly wants to win. He recently told reporters that he signed in Boston because both Cora and erstwhile general manager Chaim Bloom promised him that the Sox would be fighting for a championship. “A.C. and Chaim at that time convinced me really well that they’d definitely contend for a title that second year,” he said. The Sox still have a tiny chance to sneak into the playoffs, and shelving their closer is not exactly a path to success. That’s a whole lot of incentives for Jansen to keep pitching and for the Red Sox to let him. Pete Abraham of the Boston Globe tweeted before yesterday’s game that Jansen, “doesn’t want to go on the IL.” It doesn’t get much simpler than that, and Jansen was filmed throwing on the field soon after.

These are not easy decisions. The Red Sox aren’t just going to give up on the season, and Jansen is determined to do all he can to help them win. He's a veteran who has been around the block, and he'll be 37 in just over a week. Although just about any pitcher will tell the manager he's fine with the game on the line, few have so thoroughly earned the right to make their own decisions about their play and health. Still, there’s no universe where letting Jansen keep pitching isn’t a major risk to his long-term health. From all we can tell, both sides seem to be fine with that calculus, but that’s the reality of the situation and we should be honest about it.