Sure enough 49ers’ first-round pick Eric Reid made a rookie mistake he was lamenting after his NFL debut Sunday.

Fortunately for the hard-hitting safety it had nothing to do with his on-field play: Reid forgot to keep the ball as a keepsake after his second-quarter interception in San Francisco’s 34-28 win over Green Bay at Candlestick Park.

“I didn’t keep the ball” Reid said. “I don’t know what I was thinking but I wish I would have kept it.”

That wasn’t Reid’s only error – he also missed at least two tackles – but his six-tackle performance strongly suggested the 49ers didn’t err when they traded up to select him with the No. 18 pick in April.

Reid who defended a pass and had a special-teams tackle scooped up his interception inches from the ground after the ball clanged off the hands of Packers tight end Jermichael Finley. He also had several helmet-rattling collisions with Green Bay receivers and closed quickly to drop quarterback Aaron Rodgers for a seven-yard gain when it appeared he would scramble for a first down with less than six minutes left. Green Bay was forced to punt two plays later.

In the second quarter Reid had another interception that was nullified by a defensive offsides penalty. He saved a would-be touchdown when he jumped in tandem with wideout Randall Cobb and wrestled the ball away in the end zone.