Red Sox Infielder Isiah Kiner-Falefa Needs an MRI on His Forearm. Here’s What Went Wrong.

Isiah Kiner-Falefa was supposed to be in the Red Sox lineup Friday night against the Seattle Mariners. Then his left forearm started yelling at him louder than usual.

The veteran infielder was scratched just before first pitch because of forearm inflammation. After the game, he told reporters the issue has been nagging him for more than two weeks. It got worse during Boston’s recent homestand, and the team’s six-hour flight to Seattle apparently made things swell up even more. He skipped batting practice earlier in the week trying to limit his swings. It didn’t help.

So now he’s scheduled for an MRI. The results should tell Boston whether this is something that needs a shutdown or just a few days of rest.

Kiner-Falefa said he doesn’t think it’s serious. He expects to be back relatively soon. But anytime a versatile defender who’s been playing all over the infield suddenly can’t grip a bat, it’s worth paying attention to.

Why This Timing Hurts

The Red Sox are already piecing things together in the infield. Trevor Story went on the IL with a sports hernia on May 14, and Kiner-Falefa has been the primary fill-in. He’s started nine games at shortstop, 21 at second base, and five at third base. That kind of flexibility is exactly why Boston signed him to a one-year, $6 million deal before the season.

Without him available, the depth chart gets thin fast. Nick Sogard and Romy Gonzalez are both out. Triston Casas hasn’t played since last season. If Kiner-Falefa hits the IL too, the Red Sox may need to call up Anthony Seigler from Triple-A Worcester. Seigler was out of Worcester’s lineup Saturday, which usually means a move is coming.

The Numbers on Kiner-Falefa

Through 47 games and 119 at-bats, he’s hitting .277 with a .344 on-base percentage and a .361 slugging percentage. That .705 OPS isn’t flashy, but it’s solid for a guy who’s moved around the diamond. He’s got two home runs and 13 RBIs. Those two homers already match his total from the entire 2025 season split between Pittsburgh and Toronto.

Defensively, Baseball Savant has him in the 87th percentile in Fielding Run Value. He won a Gold Glove for a reason. The guy can play anywhere, and the Red Sox have needed that all month.

Boston’s been banged up across the board. This is just the latest headache for a team trying to stay competitive in the AL East. If the MRI comes back clean, Kiner-Falefa probably misses a few games and that’s it. If it shows something worse, the Red Sox are going to have to get creative again.