The defensive end was missing when the 49ers travelled to their NFC West rivals last season, where they lost 42-13.
The linebacker told reporters: "It was a big factor. To me, he is one of the best defensive players in this game week in, week out.
"Anytime he's not out there, we miss him. There's no question about that. We got him back now, so we know he's going to be a difference-maker for us.
"We don't want to give up 100 yards rushing. We don't want to give up 20 yards rushing. Our biggest thing is to make a team one-dimensional and that starts with stopping the run."
The two sides meet on Sunday.