It's a good thing Alex Rodriguez went for an MRI on Friday - it turns out he needed it.  In fact, he needed more than an MRI.

The Yankees All-Star 3rd baseman will undergo arthroscopic surgery to repair a slight meniscus tear in his right knee.  He is expected to be out four to six weeks.

The surgery will be performed on Monday.

Rodriguez originally suffered the injury while running the bases against the Cubs on June 19th. Rodriguez had already declared himself out of Tuesday night's All-Star Game in Phoenix.

A-Rod is hitting .295 with 52 RBIs in 80 games.  He's in the middle of the longest homerun drought of his career.  He hasn't hit a homer since June 11th (a string of 85 at-bats).

Rodriguez has 13 HR's this season - which puts him on pace for just 24.  He's had 30 or more homers for 13 straight seasons.

Eduardo Nunez will likely be the Yanks starter at third base. Nunez is hitting .278 with three home runs and 14 RBIs this season.  Ramiro Pena will also get some time at 3rd while Rodriguez is out.