Yankees general manager Brian Cashman said the discovery was made by Dr. Mark Lindsay, a world-renowned lower-half specialist who was in Tampa, Fla., to check on rehabbing third baseman Alex Rodriguez.
The weakness is a kinetic effect of Wang's right foot injury -- a Lisfranc fracture suffered last June 15 -- and may be directly responsible for the 34.50 ERA Wang posted in three big league starts this year.
Cashman said that Wang will remain in Tampa to undergo a week to 10 days of physical therapy on his hips to help build the lacking power. Asked when the Yankees might see Wang at the big league level again, Cashman responded, "I don't know."
"I know it's a minimum of 10 days to two weeks of physical therapy on the hips, and the fact that he's a pitcher, after that, who knows?" Cashman said. "He'll be able to throw to some degree, I believe, while that's going on. The main issue is to get those hips taken care of and get him back on line, because they've gotten off line."
In a corresponding move, the Yankees recalled right-handed reliever Dave Robertson from Triple-A Scranton/Wilkes-Barre, and Robertson is expected to be in uniform for Saturday's game against the Red Sox at Fenway Park.
Wang showed a mixed bag in Thursday's start against a team of Philadelphia Phillies farmhands, striking out 11 in seven innings, but also allowing five runs (four earned) on nine hits.
Yankees manager Joe Girardi said that, for a variety of reasons, there is a concern that Wang was never able to become as strong as he needed to be during Spring Training.
"His velocity was never in the 92 or 93 [mph] range that we're all accustomed to seeing, but a lot of times you chalk that up to building up," Girardi said.
One notable change from last year is that Wang has only recently been cleared to begin running between starts, instead performing all of his cardio work on stationary bicycles. That may have, in turn, affected his leg strength.
The Yankees have not announced who will take Wang's place in the rotation, but it is likely they will turn to right-hander Phil Hughes against the Tigers on Tuesday at Comerica Park.
Hughes pitched Wednesday at Triple-A Scranton/Wilkes-Barre, improving to 3-0 with 7 2/3 innings of one-run, six-hit ball in a 6-1 victory over Buffalo, walking one and striking out seven in the 105-pitch start.
"It's something that we'll continue to talk about," Girardi said.
Oddly, the Yankees have had some experience with Lisfranc injuries -- more common in other sports but a rarity for baseball players.
Brian Bruney missed three months of last season when he slipped fielding a ground ball on April 22 at Chicago's U.S. Cellular Field, but he appears to have made a full recovery, as his injury was not thought to be as severe as Wang's. First baseman John Olerud also missed the 2004 postseason with a Lisfranc injury.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.