I think he's going to play very well against the Niners.
As good as their secondary has been thus far this season (impressive 57% completion percentage against), the Rams have a group of pass catchers who are going to get mismatches on just about every down. So purely from the perspective of WRs and TEs of the Rams against SF secondary I expect them to double Quick and try to eliminate him but it's not gonna work as Davis gets through his reads and has shown a proficiency for spreading the ball around very well.
Personally I believe that Quick, Britt, Cook, Kendricks, and Bailey are more than enough to allow this kid to keep the chains moving. Get ready for another big game from the kid, IMO.