Wang was running sprints following fielding practice at the Yankees' Legends Field complex when he said he felt a "pop" in his right hamstring. The right-hander was sent for an MRI exam on Friday evening, which revealed the strain.
Wang said he hopes to be able to return to a mound in "hopefully 10 days," which may be optimistic thinking. The Yankees plan to place Wang -- who said he was "very, very sad" -- on the disabled list retroactively at the conclusion of Spring Training.
"I want to come back 100 percent," Wang said. "I hope it gets better."
A candidate to pitch on Opening Day on April 2 in the Bronx, Wang was the runner-up in last season's American League Cy Young Award voting.
The hurler tied Minnesota's Johan Santana for the league lead in victories, finishing 19-6 with a 3.63 ERA in 34 games. In four starts this spring, Wang was 1-1 with a 2.57 ERA.
"You don't want stuff like this to happen, but unfortunately, this does happen," Cashman said. "It's in front of you; you deal with it. This won't be the first and it won't be the last, unfortunately."
Cashman said that Wang's injury will open up a roster spot for another pitcher currently in Major League camp. The team still intends to carry 12 pitchers.
Right-hander Jeff Karstens would appear to be a leading candidate to join the rotation. The 24-year-old has been a standout in Spring Training, compiling nine scoreless innings before he allowed four runs in 4 1/3 innings to the Blue Jays in his last start Monday.
"We have depth and we have choices," Cashman said. "We have people who have impressed this spring. It's a short-term issue that you're dealing with. We'll wait until we get Wang back and then, in the meantime, someone else will get that opportunity."
The injury is the second this week for the Yankees, who also sidelined left-hander Andy Pettitte with back spasms. Pettitte felt the injury while performing squat exercises on Monday and has been receiving continued treatment.
"It's definitely still a little sore, but I'm a lot better," Pettitte said Friday.
The 34-year-old had originally been scheduled to pitch on Friday, but the southpaw instead was only permitted to throw softly and stretch with the team at Legends Field. He said he has been "feeling better every day."
"I've been told it's just back spasms," Cashman said. "Nobody has told me to worry about Andy, so I'm not going to worry about it right now. Obviously I'd like to see him back on the mound and throwing well, but all in due time."
Because of the scratched start, Pettitte will likely have just one more Grapefruit League appearance before the Yankees open the regular season.
He said that he would not mind pitching in a Minor League game if need be, saying that the most important thing would be to head north with the team on April 1.
"I just want to make sure I get out of here," Pettitte said. "Tampa is not the place to be."