Riley -- in a brace and with crutches -- was carted off the field to have it examined. There has been no official word from Cal concerning the extent of the injury.
"Right now, it looks a little bit more serious than just your everyday sprained knee," Cal head coach Jeff Tedford said following the game.
"He was in a lot of pain. He came off the field with tears in his eyes, and I'm sure that has a lot to do with his disappointment. He felt like it was pretty significant. Kevin is a tough guy. It's unfortunate."
Tedford says they won't know the extent of the injury until Riley undergoes an MRI, most likely on Monday.