New York Mets pitching prospect Zach Thornton will make his major league debut Wednesday night as the starter against the host Washington Nationals.

The 24-year-old left-hander was selected over more experienced options to take the place of starting pitcher Clay Holmes, who is out because of a fractured right fibula.

"[Thornton] earned it by the way he's been throwing the ball, especially at the Triple-A level," Mets manager Carlos Mendoza said this week. "We like, as a lefty against this lineup, his ability to throw strikes, his pitchability. There were a lot of names, but we decided to go with Zach."

Thornton, who is 1-3 with a 3.16 ERA over seven starts split between Triple-A Syracuse and Double-A Binghamton, is the Mets' 13th-ranked prospect, according to MLB.com. He was New York's fifth-round pick in the 2023 MLB Draft.

"I treat every game the same: I want to go out and compete," Thornton said. "I am the ultimate competitor, a strike thrower."

He'll compete in a four-game series that is tied at one win apiece. Washington, boosted by James Wood's inside-the-park grand slam, rallied from an early five-run deficit for a 9-6 win Tuesday night.

Washington will send right-hander Zack Littell (2-4, 6.10 ERA) to the mound on Wednesday. Littell, 30, will make his 10th appearance of the season.

After working behind an opener twice, he started the last time out, on Friday, and turned in his best outing of the season. He pitched five scoreless innings while allowing two hits in beating the Baltimore Orioles 3-2.

Littell rewarded manager Blake Butera's faith as he was allowed to finish the fifth inning against the top of the Baltimore order.

"It meant a lot. And I told Blake that afterward," Littell said. "I'm sure they were happy to see me get through that. But more than anything, it was proving to myself that I can go out there and get guys out in big spots. It means a lot."

Littell is 0-2 with a 3.24 ERA in eight career games (two starts) vs. New York. He gave up eight runs (four earned) on five hits (two home runs) in 3 2/3 innings in an 8-0 loss to the Mets on April 28.

Wood had two hits in addition to his first career grand slam, and Jose Tena also homered for Washington on Tuesday. Tena has hit safely in eight of his last 13 games and has six doubles, a triple, two homers, eight runs and six RBIs during that span.

The five-run comeback win matched the Nationals' largest such victory of the season.

"We just have good at-bats one through nine, guys fighting with two strikes, getting the guy over, doing all the little things," Wood said. "Getting the next guy up."

Bo Bichette hit a pair of two-run homers for New York, giving him three home runs in two games. It was Bichette's 10th career multi-homer game and the first with the Mets.

Juan Soto had two hits, including a home run, and Carson Benge had three hits for the Mets, who had won three straight games. Benge extended his hitting streak to nine games with three singles.