EUGENE, Ore. (AP) - The 21st-ranked Oregon Ducks plan to start sophomore quarterback Justin Roper when they open the season Saturday night against Washington.

The Ducks said Monday that sophomore Nate Costa's knee injury will require surgery to repair damaged cartilage, and he is likely to miss eight to 10 weeks.

Costa was the presumptive starter when fall camp began.

But last week he injured his surgically reconstructed left knee in practice.

The team said Monday that MRI results were inconclusive as to ligament damage, but that will get further assessment during his surgery.

Roper threw for four touchdowns in Oregon's Sun Bowl victory over South Florida last year and played well in scrimmages during camp this summer.

(Copyright 2008 by The Associated Press. All Rights Reserved.)