Even before his three-touchdown performance vs. Pittsburgh, Perine was putting together another solid year as RB2 for the Bengals. Everyone loves to talk about Joe Mixon, who does deserve praise for his play don't get me wrong, but Perine is still a solid running back to rely on when Mixon gets injured or just needs to take a breather for a few plays.
If you just look at his rushing yards and receiving yards, it won't tell you much. He has 434 combined yards on the season with five touchdowns (all but one are receiving). However, you have to look beyond that. If there's one thing Perine is good at, it's moving the chains, whether that be through the air or on the ground. He is responsible for 15 first downs this season, which may not sound like a lot, but considering he only comes in for usually 20 snaps on offense a game, that's pretty solid.
An underrated component for running backs is their pass-blocking ability. It's not something that people and even most experts will look out for in deciding how good a running back is. It's understandable, considering that's not going to be their duty most of the time, but getting a good block from a running back before they take off for their route can give the quarterback an extra second or two, and that can make the difference in a game.
This is something Perine is pretty good at, giving Burrow that extra second or two from a blitzing defender, or an edge that manages to get past the tackle early in the play. Next game, when Burrow is in shotgun on a pass play, try to look out for Perine in the backfield and see how much of an impact (that largely goes unnoticed) he makes.