Omar Gonzalez

U.S. defender Omar Gonzalez tries to flick the ball away from Mexico striker Javier Hernandez, who is also marked by American Matthew Besler during a World Cup qualifying game last year. (Hector Vivas / Getty Images / March 26, 2013)

Galaxy defender Omar Gonzalez, a probable starter at center back for the U.S. in this summer's World Cup, will miss Sunday's Major League Soccer match in Portland because of a left knee injury and could be out another week or more.

The injury figures to keep Gonzalez, an MLS All-Star, on the sidelines when the U.S. team's World Cup training camp opens Tuesday in Palo Alto, Calif.

Gonzalez was injured last Saturday during the Galaxy's loss in Colorado, leaving the match at halftime.

Galaxy Coach Bruce Arena said he believes Gonzalez will be able to report on time to the World Cup camp, but it's uncertain when he'll be able to participate in training.

Gonzalez, 25, had surgery in January 2012 for a torn ligament in the knee and returned that July 4.