Rookie tight end Vance McDonald likely won't play Friday because of an undisclosed injury that's kept him out of practice since the exhibition opener. . . . Rookie cornerback Marcus Cooper intercepted a Kaepernick pass intended for Kyle Williams. . . . Linebacker Aldon Smith jogged with a trainer into the locker room early in practice for an apparent hand injury. He returned after 30 minutes and showed no signs of injury while excelling in team drills. . . . While Carlos Rogers rested, fellow cornerback Tarell Brown returned to practice after missing the past two sessions with an unknown injury. Still out were left tackle Joe Staley (unknown), linebacker Patrick Willis (hand) and safety Bobby Ventrone (hamstring).