WASHINGTON -- The Nationals optioned third baseman Carter Kieboom, their No. 1 prospect per MLB Pipeline, to their alternate training site in Fredericksburg, Va., on Wednesday.

Kieboom, 22, transitioned from shortstop to the hot corner as the team looked to fill the vacancy left by Anthony Rendon in free agency. The Nats gave him the opportunity to earn the starting role in Spring Training, and he has been platooning at the position with 14-year veteran infielder Asdrúbal Cabrera as Kieboom gets acclimated in his first full Major League season. Cabrera was in the starting lineup at third in Wednesday's 3-2 loss against the Phillies at Nationals Park.

“I told [Kieboom], ‘Hey, you’re going to be our third baseman,’” manager Dave Martinez said. “‘We just want to get you right. We want to get your swing right. You’ve been playing third base really, really well.’ I mean, he has really played well. ‘Just go there, get your swing right. As soon as we deem that you’re ready and you’re back to who you are -- which is a guy that drives the ball to left-center field, drives the ball to right-center field, squares balls up -- then you’ll be back here playing third base. So keep your head up.’”

Kieboom has slashed .200/.359/.200 with 10 hits and five RBIs in 17 games. He has been exhibiting patience at the plate, drawing 11 walks in 64 plate appearances, but he also has struck out 20 times. On Tuesday, Kieboom went 0-for-4 and grounded into two first-pitch, inning-ending double plays. Martinez noted that Kieboom had been “struggling” and he wanted to protect the young infielder. 

“I felt like, yesterday, he was really playing more for results,” Martinez said. “When you start doing that, you start getting frustrated when you don’t get the hits. We sent him down; he’s going to get tons of at-bats.”

Defensively, Kieboom has a .978 fielding percentage with one error over 132 2/3 innings. The Nationals tasked him during the shutdown with improving his footwork at his new position.

Cabrera, 34, has been a reliable utility player, stepping in at both third and first base, while also serving as the designated hitter. He has yet to make an error on his 20 chances at third base over 94 1/3 innings this season. Cabrera went 0-for-3 with one walk and one run Wednesday, and he is batting .260/.333/.490 with five homers and 17 RBIs in 96 at-bats.

Utility man Josh Harrison could see playing time at third base while Kieboom is in Fredericksburg, especially on days when Cabrera gets a game off or is playing a different position. Harrison has played one game at third this season, and he has 1,863 2/3 innings of experience at the hot corner, with a .964 career fielding percentage. He has played just nine innings at third base over the last three seasons, however, instead logging the bulk of his playing time at second base.

Howie Kendrick is also an option, but the Nats have been cognizant of his playing time after he experienced tightness in his hamstrings. Kendrick, who has played 231 1/3 frames at third over his career, has been utilized exclusively at first base or as the DH this season.

Doolittle reinstated
Left-handed reliever Sean Doolittle was reinstated from the 10-day injured list (right knee fatigue) on Wednesday. Doolittle has struggled this season, accumulating a 15.00 ERA while allowing three home runs over three innings in his five outings. He joins No. 24 prospect Ben Braymer as the only southpaws in the bullpen.

Surgery and recovery updates: Strasburg, Romero, Castro
• Right-hander Stephen Strasburg underwent surgery on his right hand to alleviate carpal tunnel neuritis on Wednesday. The Nationals’ goal is for the reigning World Series Most Valuable Player Award winner to be ready for Spring Training in 2021. Because of protocols this season, players on the IL cannot rehab at the home ballpark.

“He’s got to kind of stay away at another site,” Martinez said. “Until he gets ready to do baseball activity, that’s all he can do. It’s definitely different. Before, we’d have him here with us -- the days when we’d go on the road, we’d keep one of our trainers back and they’d be rehabbing here.”

• Left-hander Seth Romero, Washington’s No. 11 prospect, will have a pin placed in his broken right hand, an injury that he sustained this weekend. Because the injury is to his non-pitching hand, the Nats hope he can continue his throwing program while he recovers at the alternate training site. Romero made his Major League debut on Aug. 13 after working his way back over the last two years from Tommy John surgery.

• Starlin Castro is at his home in Miami rehabbing from surgery to repair his fractured right wrist. The second baseman has expressed enthusiasm on a quick return -- first by aiming for the playoffs, and most recently, suggesting a three-week recovery. On Monday, Martinez recounted telling him, “'When you get back, we’ll welcome you in like we did before, and you’ll be ready to go. But take it easy. You just got a pin put in your hand.'”