Beyond that, Mack's performance had a transformative effect on his teammates. One of them was fellow outside linebacker Leonard Floyd, who had his best, more consistent season as a pro in 2018.
Floyd, 26, has been the pass rusher that the Bears envision when they selected him ninth overall in the 2016 draft, but he's been really good in his own right. He entered the NFL with rare speed and athleticism but lacked the strength, power and technique to play at the level that the Bears hoped initially. Injuries also slowed his progress across his first two seasons.
Floyd was much improved in 2018, coming into his own. He proved he's a strong run defender, a better one than the Bears thought that he'd be. Floyd showed strength at the point and set the edge when playing the run.
His pass coverage skills are also good, which allowed Floyd to blossom into a good all-around player. He may never produce double-digit sacks -- Floyd only had four in 2018 -- but on this defense with more growth, he should consistently get eight or nine.
Behind those two, the Bears' depth is solid but not great. Aaron Lynch was the third outside linebacker in 2018, and he had his strongest season since 2015. He's a good run defender and better-than-adequate pass rusher. Lynch had three sacks last season.
After he didn't receive much interest from other teams on the free-agent market, he re-signed with the Bears. His new deal isn't as lucrative as his last one with the Bears, as durability has been an issue. He should be a valuable member of the team's rotation.
Isaiah Irving also received a fair amount of playing time last year and has shown improvement year to year. The question the coaches must ponder is whether he's reached his ceiling. If he has, he figures to be hard-pressed to make the roster.
The Bears selected Kylie Fitts in the sixth round in 2018. He flashed in the preseason but didn't impress once the season started. Fitts has the athletic traits that coaches covet, but his play has been inconsistent. He has to prove in training camp this year that he's more than just an adequate special teams player.
The Bears signed two undrafted free agents who could challenge for a roster spot in camp. One is Canadian college prospect Mathieu Betts from Laval College. He dominated Canadian college football last year and finished his career with 35.5 sacks. He has an explosive first step as well as good hand use but outside of the East-West Game has never played American football. He has talent, but he's raw, so his progress will be interesting to track.
The other undrafted free agent who will be interesting to watch is Chuck Harris from Buffalo, the same school that produced Mack. Harris had a combined 10.5 sacks over the last two seasons. He missed three games and parts of three others in 2018 because of an arm injury, which may be why he wasn’t drafted. At 6-foot-4 and 255 pounds with 4.70 speed, he has good outside linebacker traits. At Buffalo, he was strictly a 4-3 defensive end, so he will need time to learn to drop and play in coverage.
A final player who could challenge for a roster spot is James Vaughters, a Chicago native who played at Stanford. He signed with the Packers in 2015 but was cut at the end of the preseason and landed on the practice squad. He also spent time with the Patriots and Chargers before going to the Canadian Football League, where he was one of the top defenders. Vaughters was consistent against the run and pass, and he's regarded as a good special teams player.
Overall, the Bears' two starters are as good as they come in the NFL. The depth is good but not great, so that will be a storyline to follow as OTAs continue and training camp approaches. There are some young players with talent, but they still have to prove they're worthy of making an NFL squad and contributing.