Bears need outside linebacker Khalil Mack to light it up once again

Outside linebacker Khalil Mack was a force of nature in his first season with the Bears in 2018 and has something to prove this season.When it comes to star players, you don’t know when to start worrying.

Outside linebacker Khalil Mack, 29, is starting his seventh season in the NFL, and three things are possible: He could be getting better, sitting at a plateau or riding his way down.

You hope it’s not the third because the Bears need him to be the stud he once was.

You hope it’s not the middle, either — the plateau — because last season wasn’t great by Mack’s standards.

His 81⁄2 sacks in 2019 were the lowest of his career, other than in his rookie season with the Raiders in 2014, when he still…