CARSON, Calif. -- Chivas USA defender Jonathan Bornstein will miss six weeks because of a partially torn left knee ligament.

He was injured Thursday during practice, and an MRI exam later revealed a partial tear of his medial collateral ligament, the team said Friday.

Bornstein has started and played full 90-minute games against Denmark and Mexico since being called up to the U.S. national team in January. He scored in his international debut against Denmark.

He had six goals and four assists in 34 games for Chivas last season, when he was named MLS rookie of the year. Chivas USA opens its season April 7.