Celtics guard Ray Allen suffered an eye injury during a routine drill on Saturday.

Allen was supposed to take the ball from Kendrick Perkins on a hand-off drill. Instead, Allen was laying on the ground grabbing his eye.

"It was a post pass and cut," Rivers told the Boston Globe. "Perk was supposed to hand off low and Perk was going to fake it and go high. Unfortunately, he did it too late."

"You couldn't see it, then all of a sudden he's laying down. Then you saw the blood and you're saying, 'Oh no, I don't think he's faking.' "

Allen suffered a cut above his left eye that required five stitches at New England Baptist Hospital.

"He got hit pretty hard in the head and went down," Rivers said. "I'm sure he had a buzz or something."