His 138 games were his fewest since 1999, when he tore the medial meniscus in his left knee during a spring training agility drill on March 30. He played in the first two games of that season with Seattle, then was put on the disabled list April 7 and missed 32 games until he returned May 14.

Dr. Struan Coleman of the Hospital for Special Surgery, which treats the New York Mets, said Rodriguez probably could avoid an operation by having heat and cold treatment, but might need an injection to control pain and/or inflammation. Coleman said it is unlikely the injury is related to past steroid use.

"It's quite common in athletes who do a lot of rotational movement in their sport," Coleman said. "This a slowly progressive process. This has been going on a number of years."

If it turns out Rodriguez will miss a significant portion of the season, the Yankees could pursue Mariners third baseman Adrian Beltre, the Orioles' Melvin Mora, or the Blue Jays' Scott Rolen.

The leading internal candidate to replace Rodriguez is Cody Ransom.

"It's worrisome thinking about your club without Alex," Yankees manager Joe Girardi said. "Alex hasn't had any pain. Shocked. I think that's a pretty good way to describe it."

Other options include the Yankees trading for A's shortstop Bobby Crosby, who is earning $5.25 million this season, or signing Damion Easley or Mark Grudzielanek as a free agent.