PHOENIX — Brewers starter Yovani Gallardo has torn cartilage in his left knee and is expected to miss the first four weeks of spring training.

Gallardo will return to Milwaukee tomorrow and have the arthroscopic procedure Tuesday. He then will return to the Brewers' camp to begin physical therapy.

Brewers spokesman Tyler Barnes said Sunday the right-hander had discomfort a few days ago after a throwing session. His knee swelled up afterward.

The 22-year-old Gallardo, expected to be a main cog in the Brewers rotation, was 9-5 with a 3.57 ERA in 20 games last season, including 18 starts.