The Season Is Likely Over for Triston Casas

The Boston Red Sox dropped to a .500 record over the weekend, but that bit of unpleasantness was overshadowed by the loss of starting first baseman Triston Casas to a serious knee injury. Running to first during the first of a three-game set against the Twins on Friday, Casas collapsed suddenly while trying to beat out a slow roller fielded by the pitcher, Joe Ryan. It was revealed on Saturday that Casas had ruptured his left patellar tendon, and on Sunday he underwent surgery. Without Casas, the second-place Sox have to reconsider their short-term options at first base, ideally before they fall too far behind in the AL East.

Boston could find no cause for optimism to put a positive spin on what happened. Chief baseball officer Craig Breslow came right out and said the team doesn’t anticipate Casas to return in 2025. So, if you were hoping the first baseman might sneak back in time for the playoffs, that appears to be highly unlikely.

So what does this mean for Casas? Well, from a baseball standpoint — rather than a rehabilitation one, as I’m even less qualified to make medical pronouncements than Dr. Nick Riviera — coming into the season, ZiPS saw Casas as a solidly average first baseman, with a projected slash line of .246/.350/.462, a 125 wRC+ and 1.6 WAR. That last number was on the low side simply because ZiPS projected him to play in only 108 games, partially due to his being platooned in the past but also owing to his history of injuries. I expressed some concern about his profile in the preseason because of his struggles with making contact.

Casas was off to a slow start this year, hitting .182/.277/.303 with a bleak 58 wRC+. That’s worrisome for any player, but even more so for a platoon first baseman without much defensive value. All 27 games he started this season came against a righty. April’s gonna April, but the bad start did put a bit of a damper on his long-term outlook. Crank out some projections, ZiPS-o-Matic!

Without factoring in his injury, Casas’ struggles to start 2025 caused a clear drop-off in his next-five-years projections, though I don’t personally think it was enough to fundamentally change our perception of him. He’s still a power-hitting first baseman you’d be happy to have in your lineup, but he’s not a major star to build around. As an aside, ZiPS is far less worried than the Red Sox are about letting Casas face left-handers; he is projected for a .226/.317/.395 line against southpaws in 2026. That’s not ideal, but it’s also not an unusually large platoon split for a left-handed slugger.

ZiPS is aware of injuries, but mainly in hindsight; it factors in the time missed after the fact because I don’t like being the position of diagnosing current injuries. But in this case, because we know that Casas’ rest-of-season projection is almost certainly going to be zero plate appearances, I don’t mind breaking the rules and telling ZiPS that 2025 is over and Casas missed more than 100 games with a knee injury.

As you can see, the season-ending injury has slightly soured his projection. But if there’s a silver lining here, it’s that Casas’ game isn’t really based on speed, meaning that ZiPS expects the overall long-term impact of the knee injury to be less for him than it would be for a faster runner. By contrast, when I run the same projection for Jarren Duran after giving him a serious knee injury — Sorry, Jarren! — his projected 2026 WAR declines from 3.5 to 2.2 WAR.

Casas ought to be back in 2026, but the Red Sox have to answer the question of what to do at first base for the next five months. Romy Gonzalez has been Casas’ platoon partner this year, and at .327/.382/.449, he’s hit well in his 55 plate appearances as of Monday morning. But he’ll probably lose a hundred points or so from his current .421 BABIP, so it’s unrealistic that he’ll keep up that line. That said, he has been making hard contact this season, with a hard-hit rate approaching 60%, up from 50% last year, meaning that his production is not a stone-cold fluke, either. ZiPS projects Gonzalez to post a 107 wRC+ the rest of the season, a reasonable performance for a Plan B first baseman, but the Red Sox should be a bit more ambitious than settling for reasonable, especially when the player in question is more of a substitute utilityman than a true first baseman.

But whom should they target then? That’s the harder question. Rafael Devers would seem to be the likely internal option, and the team hasn’t explicitly ruled that out, but I wouldn’t be surprised if the Red Sox decided not to switch his position again considering how he responded when they moved him off third base after signing Alex Bregman. In this case, perhaps discretion is the better part of valor. Boston also does not appear to be inclined to temporarily move to prospect Roman Anthony to first base.

Outside the organization, pickings are slim at the moment, as few teams have completely given up on the season. Andrew Vaughn is probably available, and his peripherals suggest that he’s performed better than his actual numbers during his brutal start, but I’m not sure Boston really wants a reclamation project here. The recently demoted Jake Burger would result in the same objection. If the Nats are interested in trading Nathaniel Lowe, he may be the best option out there, and he’s not a free agent until after next season, though that might make them less likely to move him. And the Brewers probably aren’t yet at a point where they’d let go of Rhys Hoskins for cheap. Anthony Rizzo is still a free agent, and Jon Singleton is now in Triple-A with the Mets, but if those are the two best options out there, I think the Red Sox would be better off just rolling with Romy. (I want to see Marcelo Mayer get some time at first, but that’s mostly so I can make some kind of lame Romy and Marcelo’s High School Reunion joke.)

The injury to Casas doesn’t doom his future outlook too much, nor does it shatter Boston’s chances to contend this season, but the Red Sox need to decide what they want to do here fairly quickly. Sure, the impact of any first base move would be limited, but even a marginal upgrade could make a difference in a tight AL East race.