Costa, who tore ligaments in the knee last October, had an MRI following his latest setback but results proved inconclusive with regard to ligament damage. The status of his anterior cruciate ligament (ACL) and medial collateral ligament (MCL) will be assessed during the upcoming surgery. A date has not been set.
The Hilmar, Calif., product began Fall Camp atop the Oregon depth chart but was splitting first-team reps with fellow redshirt sophomore Justin Roper at the time of his injury.
The lanky 6-6 Roper, who passed for a record four touchdowns in last season’s Sun Bowl victory over South Florida, will take over the No. 1 spot for now with a stiff challenge expected from sophomore transfer Jeremiah Masoli.
Oregon opens its 2008 campaign with a Pac-10 home game versus Washington on Saturday at 7 p.m.