By early Thursday afternoon, Chien-Ming Wang had reached a new pinnacle in his return from baseball’s brink. For two innings, he carved up his old team with a revived, cannonball sinker and a slider teammates had never seen him throw better. Groundouts and whiffs further entrenched his place in the Washington Nationals’ crowded rotation.

“It just reaffirmed the fact that he’s back,” Manager Davey Johnson said.

In an instant, one cruel, slow-rolling groundball threatened to curtail Wang’s three-year recovery. Wang exited his start after he strained his left hamstring while fielding the ball and running to tag first base. Wang, 31, left Space Coast Stadium before the game ended to receive further tests. The Nationals expected to receive the test results Friday morning, leaving them clinging to the hope Wang will not require another extended rehab.

“He’s been throwing his butt off,” said John Lannan, the starting pitcher who figures to replace Wang in the event the injury sidelines him. “Hopefully, he’s okay and he can make his next start. You hope and pray that he didn’t do anything.”

Last July, Wang made his first start after he missed two years recovering from a torn capsule in his right shoulder and the unique surgery it required. Pitching with multiple screws in his shoulder, Wang showed the Nationals enough to re-sign him to a one-year, $4 million contract and slot him in their rotation.

Wang had looked sharp all spring, especially in the early innings Thursday against the New York Yankees, the team with which he became a star before injury sidetracked his career. Wang allowed no runs in 22 / 3 innings, striking out four and allowing two balls out of the infield. He threw his sinker between 90 and 93 mph, surpassing his average velocity from last year.

Wang struck out the first batter he faced, Brett Gardner, watching a backdoor slider that curled over the plate’s outside edge. “His slider and his breaking stuff is a lot better than it used to be,” said reliever Tyler Clippard, also a teammate of Wang’s in New York.

With one out in the third inning, Russell Martin dribbled one of Wang’s sinkers to the right side. The Nationals had practiced tricky rollers like it all spring. Coaches teach pitchers to run on a line to first base and field the ball if they can. Wang scrambled to glove the ball. First baseman Chad Tracy stood behind him in case the ball scooted by Wang.

“That’s probably one of the tougher plays there is,” Tracy said. “He did the right thing.”

Wang took a false step when he saw Tracy would not be covering first base. Tracy saw Wang roll his ankle. Wang’s leg straightened and his knee buckled, and then he crumpled to the ground.

“You could see his leg quivering,” Tracy said. “He didn’t want to put any weight on it. You could tell he was hurting.”

Sprinting to the base, Martin leaped over Wang as the right-hander writhed in the dirt.

“I asked him if he was all right,” Martin said. “He kind of shook his head like, ‘I’m not feeling too good.’ It happened in slow motion. It was weird.”

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

“I could tell right away when he got up and he was limping, that was it for him,” Johnson said. “I hope it’s not serious.”

In June 2008, while running the bases, Wang partially tore a tendon in his right foot and badly sprained his 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 shoulder capsule tear.

“When there’s running involved, it’s tricky for him,” said Yankees Manager Joe Girardi, who managed Wang in 2008 and 2009. “And he looks athletic, that’s the problem.”

The Nationals originally signed Wang in February 2010, hoping he could pitch by the middle of that season. A series of setbacks derailed him. He remained at the Nationals’ complex in Viera, sweating through daily rehabilitation. Nationals left-hander Ross Detwiler joined him as he rehabbed after hip surgery.

“My rehab was three months, and I was going crazy the whole time,” Detwiler said. “I couldn’t imagine two years. I could kind of see the light at the tunnel. For him to be able to bear that and keep his nose on the grindstone and work hard the whole time, it says a lot about him.

Even if Wang’s hamstring strain heals quickly, it could detour him. He would have to prevent falling into bad mechanical habits to protect his shoulder. If Wang misses time, it will be multiplied by the need to rebuild strength in his shoulder. The Nationals have already brought Wang along slower than the rest of the rotation as a precaution.

The Nationals have a more-than-capable replacement in 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 Gonzalez left Lannan, twice the Nationals opening day starter, on the outside looking in.

The Nationals’ pitching depth could not console their hurt for Wang. Just as he reached a new milestone, he faced the prospect of another long road.

“He’s been battling a few years to get back,” Tracy said. “He’s a great guy. Hopefully, he’s all right.”