Michael Smith and Jemele Hill react to 49ers QB Colin Kaepernick's struggles and Packers LB Clay Matthews' insult that Kaepernick "ain't Russell Wilson." (1:50)

SANTA CLARA, Calif. -- Colin Kaepernick didn't play like an elite quarterback on Sunday against the Green Bay Packers, and the struggling 49ers starter heard about it -- not just from the booing fans at Levi's Stadium, but also from one of his opponents.

TV cameras on the Fox broadcast picked up sound of Packers linebacker Clay Matthews shouting at Kaepernick: "You ain't Russell Wilson, bro."

It happened during the fourth quarter of Sunday's 17-3 win by the Packers.

That came after Matthews sacked Kaepernick in the third quarter and mocked his trademark biceps-kissing celebration.

Matthews said after the game that the celebration was all in fun.

"Nah, it's not planned," Matthews said. "I was going to hit him with the predator, and then I had a light bulb go off in my head. It's just having fun. We're a bunch of kids out there running around and having fun at each other's expense."

Clay Matthews mocked Colin Kaepernick's bicep-kissing celebration after sacking the 49ers QB in the third quarter. "I was going to hit him with the predator, and then I had a light bulb go off in my head," Matthews said. Thearon W. Henderson/Getty Images

However, Matthews was not asked about the Wilson comparison.

Kaepernick finished 13-of-25 passing for 160 yards and an interception. He rushed for 57 yards on 10 carries.