Kieboom sitting tonight after jamming left thumb

Carter Kieboom is not in the Nationals lineup tonight after jamming his left thumb sliding into second base in the ninth inning of Monday night's loss in Miami.

"Yesterday he got beat up a little bit, hurt his thumb a little bit," manager Davey Martinez said during his pregame Zoom session with reporters. "So we're just going to give him a day. And if we need him later on, we could use him."

Kieboom had a pair of tough slides during the game. He barreled into Marlins pitcher Zach Thompson while scoring on a wild pitch in the top of the seventh, his helmet hitting Thompson's knee. Then, two innings later while trying to steal second, he jammed his left thumb into the base as the throw hit him.

The 23-year-old third baseman finished out the game but didn't see any action the rest of the way in the Nats' 8-7, 10-inning loss. With the thumb still sore afterward, he's sitting tonight as a precaution.

"He slid a couple times, and the last time he slid at second base, he got hit with the ball," Martinez said. "He wears that wrist guard, but he jammed his thumb back. It was sore last night. I talked to (director of athletic training Paul Lessard), and I said let's just give him a day and let him go through his routine. And if he feels OK, then we can use him off the bench."

Jordy Mercer will start in Kieboom's place at third base, the latest in a string of recent starts for the veteran infielder since returning from a lengthy stint on the injured list with a calf strain.

Kieboom's injury came at the end of a night in which he reached base three times (one walk, two hit-by-pitches). It was a welcome performance after a tough stretch that has seen him go just 2-for-33 with zero extra-base hits. His batting average across 212 plate appearances is down to .213, his slugging percentage only .333.

"He's starting to get a little bit long with his swing," Martinez said prior to Monday's game. "I think we just need to slow his feet down a little bit and get him back toward the middle of the field. He was hitting the ball really hard there for a while. We've just got to get him back zoned into the middle of the field and shorten his stride. His feet are moving way too fast. We've got to get him to slow down a little bit."