At training Tuesday, Los Angeles Galaxy head coach Bruce Arena confirmed that Brazilian centerback Leonardo is probably out for the season with a knee injury.

In the final seconds of a 2-1 victory over Chicago Sunday, Leonardo collided with Fire attacker Patrick Nyarko and fell to the ground clutching his knee. Torn anterior and lateral cruciate ligaments in his right knee was the diagnosis, and Arena said he will have surgery in about a week.

“Those things happen," Arena said. "You can never understand why they happen. Unfortunately, it’s all part of the game, but we’re going to do everything we can to get him back on the field and work with him. I’m confident he will be back on the field with the Galaxy.

Sean Franklin or A.J. DeLaGarza have played in the middle alongside Omar Gonzalez and could replace Leonardo. Veteran Gregg Berhalter, who has yet to play this season, is another possibility.

Landon Donovan, who missed the team's three-game road trip with an inflamed knee, resumed training Tuesday. Arena expects him to be available for Saturday's home match against Portland.