LOS ANGELES (AP) - UCLA guard Tyler Lamb will undergo arthroscopic left knee surgery on Tuesday and is expected to be out 4-to-6 weeks.

The school announced the surgery Sunday night, but didn't explain how Lamb got injured.

The junior from Santa Ana, Calif., averaged 9.0 points, 3.6 rebounds and 2.8 assists playing in all 33 games last season. He missed a month after having a similar procedure on the same knee in July 2010, the summer before his freshman year.

Bruins coach Ben Howland says he's optimistic that Lamb will return in four weeks.

Lamb played in all three of UCLA's games on its China tour in late August.

The Bruins open the season on Nov. 9 against Indiana State.