Washington Nationals righthander Chien-Ming Wang suffered a strained left hamstring in Thursday's spring training game against the New York Yankees.
The team sent Wang to undergo additional tests after he was hurt while attempting to cover first base.
The 31-year-old Wang had problems putting weight on the leg after the mishap.
Wang had a solid comeback season in 2011 after missing the entire 2010 campaign with shoulder problems, going 4-3 with a 4.04 ERA in 11 starts. He had signed a one-year contract in November.
Wang spent his first five seasons with the Yankees, emerging as one of the club's top hurlers. He posted back-to-back 19-win campaigns in 2006-07 but has just 13 victories since.