Wang, the favorite to become the Nationals' fifth starter, left in the third inning of Washington's 8-5 loss to the New York Yankees on Thursday with a strained left hamstring.
Fielding Russell Martin's grounder near first base, Wang stumbled then fell. As he was falling over first base, his leg went up in the air and was brushed by Martin as he ran through the base.
"I fell on my left shoulder. I'm fine," Martin said of the play. "I asked him if he was OK and he shook his head."
Nationals manager Davey Johnson said Wang would undergo more tests to determine the severity of the injury. Johnson was told by team trainers it appeared Wang was hurt as he bent down to pick up the ball.
Washington first baseman Chad Tracy said Wang had a choice of either trying to field the ball or letting it go by and hoping Tracy could toss it to him at first in time.
"That's probably one of the tougher plays that there is," Tracy said. "It's tough to judge off the bat. We're taught in spring training if the pitcher can get that ball, then get it and keep going. He did the right thing, just something happened to throw him off balance."
Wang had been off to a strong start, allowing two hits and striking out four through 2 2/3 innings. It was his first start against New York, where he spent five seasons and twice won 19 games for the Yankees before being slowed by a foot injury in 2008. In 2009, he had shoulder surgery and has spent the better part of three years trying to regain his form.
"Anytime you see one of your teammates have an injury, you feel bad for him, especially (Wang)," Tracy said. "He's been battling for a few years to get back. He's a great guy. Hopefully, he's all right. Hopefully, he doesn't miss a lot of time."
Michael Pineda, meanwhile, gave up two runs and four hits in 3 2/3 innings for New York. He retired the first seven batters. Catcher Jhonatan Solano had an RBI double in the third and designated hitter Adam LaRoche added a run-scoring double in the fourth.
Pineda threw 65 pitches, 41 for strikes.
He was particularly excited about the development of his changeup, a pitch the Yankees have said he needed to compliment his fastball and slider.
The right-hander, acquired in a trade that sent top prospect Jesus Montero to Seattle, should be the Yankees No. 3 or 4 starter this season. But nothing is a lock. He came into camp overweight and the overpowering fastball that helped make him an All-Star as a rookie last year has yet to reach the mid-90s, which is what he was throwing last year with the Mariners.
"Last year, I didn't throw a lot of changeups," he said. "This year, I focus a little more on my changeup, make it a good pitch all the time. I'm not worried (about) my fastball. I don't know how my fastball is right now, but it feels good."
Yankees shortstop Ramiro Pena sustained a sprained right ankle while trying to steal second in the fourth inning.
First baseman Jose Gil also had two RBIs for New York. Tracy and shortstop Steve Lombardozzi each had two hits for Washington.
Nationals left fielder Michael Morse didn't take part in any team activities Thursday as he recovers from a strained lat muscle. Johnson said one again that he's not concerned about Morse's injury . LaRoche was Washington's designated hitter Thursday, while Chad Tracy played first base. Johnson joked that the idea came from LaRoche's son. "Drake said he needed to DH, and not play (in the field)," Johnson said. When asked, "Are you taking orders from a 9-year-old?" Johnson cracked, "Yeah, and so does his dad." Johnson said he wanted to get LaRoche some at-bats and wanted to see more of Tracy, who is competing for the team's final bench spot. . Nationals catcher Wilson Ramos is scheduled to be the designated hitter Friday in Tampa against the Yankees. Ramos has missed the past two games with a heel injury sustained Tuesday night against Detroit . The Nationals trimmed their spring training roster to 41 following Thursday's game by optioning right-handed pitcher Yunesky Maya to Triple-A Syracuse and outfielder Eury Perez to Double-A Harrisburg. The team also assigned right-handed pitchers Jeff Fulchino and Waldis Joaquin to minor league camp . Yankees right-hander Freddy Garcia will likely miss his next start after getting hit on his right hand during Wednesday's game against Toronto. "The swelling went down, but there's still swelling in there," Girardi said. "(His next start) would be Tuesday, but I still don't know if he'll make it. I guess we'll know a lot more in the next 48 hours." . Girardi said he talked to Nick Swisher Wednesday night, after the outfielder had left Wednesday's game with tightness in his groin. Though he didn't know the severity of the injury, Girardi said the sense he got from Swisher was that if it had been the middle of the season, Swisher would be able to play . Reliever David Robertson, recovering from a bone bruise in his right foot, was scheduled to play catch in Tampa on Thursday . Yankees utility man Eduardo Nunez, who has been dealing with a bruised right han d, is not expected to pick up a bat until Saturday. Nunez was scratched from the lineup prior to Tuesday's game against Boston.