(Julio Cortez/AP)

The Nationals signed Wang this November to a $4 million contract, and he entered spring as the fifth starter in a crowded Nationals rotation. Wang had looked all spring, especially in the early innings today against the New York Yankees, the team with which he became a star before a major shoulder injury sidetracked his career.

Last July, Wang made his first start after he missed two years rehabbing from a torn capsule in his right shoulder and the major surgery it required. He showed the Nationals enough to re-sign him, going 4-2 with a 3.70 ERA in his final 10 starts.

Today, Wang allowed no runs in 2 2/3 innings, striking out three and allowing only two balls out of the infield. He threw his sinker between 90 and 93 miles per hour, surpassing his average velocity during his 2011 return.

With one out in the third inning, Russell Martin dribbled one of Wang’s bowling ball sinkers to the right side. Wang scrambled to pick it up. He took a false step when he realized first baseman Chad Tracy, having gone for the ball, would not be fielding first base. Wang’s knee buckled, and he collapsed to the ground.

Head athletic trainer Lee Kuntz and Manager Davey Johnson bolted from the dugout. Wang stood up, then immediately limped to the dugout and back to the Nationals’ clubhouse.

In June 2008, Wang partially tore a tendon in his right foot and badly sprained his right ankle, which sidelined him for the remainder of that season. The injury led to altered mechanics when he returned in 2009, which contributed to his right shoulder capsule tear.

If Wang misses time, the Nationals have a more-than-capable replacement in John Lannan, who had been drawing trade interest from across the league. Last year, Lannan won 10 games and posted a 3.70 ERA in 33 starts, but the Nationals’ signing of Edwin Jackson and trade for Gio Gonzalaez left Lannan, twice the Nationals’ opening day roster, on the outside looking in.

The Nationals were not eager to trade Lannan so early in the spring in order to maintain the depth of their rotation in case a starter suffered an injury. They knew that sometimes, in baseball, crowded pitching rotations sometimes work themselves out. Whether that is the case with Wang, though, remains to be seen.