The 49ers don't seem thrilled to face Philip Rivers

"I actually got to talk to (Rivers) a little bit last week," Shanahan said on Monday. "He was talking with (49ers assistant head coach) Gus Bradley. He has a good relationship with Gus being together with the Chargers.

"Gus came down to my room, and I got to talk to him a little bit. I was telling him how cool it would be (for him to come out of retirement), but about 10 seconds into it, I realized we were playing against him in 10 days, so I tried to sway away from that and tell him how dumb it would be. It didn't work."

To be clear, Rivers is well past his prime. Against the Seahawks on Sunday, he threw for just 120 yards and 1 touchdown. He can't beat the 49ers on his own -- he'll lean on Jonathan Taylor, one of the best running backs in the NFL. Stopping him will be 49ers' top priority.

But Rivers is crafty, even at his age. The Seahawks sacked him only once, and that's because he can read defenses, hit his check-downs and throw the ball away. Plus, he's not afraid to take a hit.

"I admire the hell out of him," Shanahan said. "What he did (on Sunday) -- he obviously gave his team a chance to win. But the way he plays and the style he plays with, I respect him as much as any quarterback I've ever studied over the last 20 years.

"What I admire the most is to be someone at that age and come in there and want to play the right way, which to me is hanging in that pocket and taking some of those hits. That's something that gets very old fast to a lot of people. For him to still have that toughness and that competitiveness, he's not going to get into anything unless he's all about it, 100-percent in.

"That's why he made the decision. That's why I think he's giving them a good chance to win and helping their team."

Shanahan knows that Rivers won't beat himself -- the 49ers will have to beat him. And that means their offense (read: Brock Purdy) must play a mistake-free game.

It's never a good look when you lose to a grandpa.