The right-hander fielded a slow roller by Martin and tried to make the play at first base. Wang stumbled toward the bag and fell as he was touching the base. The pitcher's leg went up in the air and was hit by Martin, who was running up the line.
Wang walked off the field under his own power.
"Hopefully, it's not serious," Nationals manager Davey Johnson said. "(Wang) was having a great spring, trying to come back to what he was. So you hate to see something like that.
"He was having a great outing. He was throwing the heck out of the ball. He was pitching at 90-91 (miles per hour), and he hit 93. He was just outstanding."
Johnson said the team was awaiting test results on Wang but said he wasn't certain what type of tests he was undergoing.
Wang spent five years with the Yankees and won 19 games in 2006 and 2007.
Information from The Associated Press was used in this report.