Bears running back David Montgomery returned to practice Thursday for the first time since hurting his knee Oct. 3 in a win over the Lions.

The Bears will now have 21 days to activate the 2019 third-round pick from injured reserve. After rushing for 309 yards and three touchdowns in the first four games this season, Montgomery has missed the last four contests.

"I know he's worked really hard to get to this point," said coach Matt Nagy. "It probably feels like forever to him, and I know it feels like that for us, too. He was having such a great year, so now we'll see where it goes. 

"But it's good timing if we are able to get him back and get him going because also, too, he's grown into such a tremendous leader for that offense, and … when you're not around as much, the guys, you miss that. And now to be able to get him back in those huddles and that stuff is great."

What Montgomery shows this week on the practice field will determine whether he's ready to return to action Monday night against the Steelers in Pittsburgh. The Bears have a bye the following weekend.

"We'll keep an eye on where he is and we'll see how he looks," Nagy said. "That will be key, to see how he looks … If he's able to go and we feel good about it, he will be up and ready to rock and roll."

While Montgomery ranked fifth in the NFL at the time of his injury, the Bears running game hasn't skipped a beat without him. Rookie sixth-round pick Khalil Herbert has helped fill the void, rushing for 344 yards in the last four games, the fourth most by an NFL running back over that span.

Nagy told reporters Thursday that when Montgomery returns, he will reassume his role as the Bears' No. 1 running back.

"You guys all know how we feel about him and what he's done," Nagy said. "He's a tremendous leader on this offense."

In other injury news Thursday, Nagy said there's no change in Khalil Mack's status. The six-time Pro Bowler did not practice Thursday due to a sprained foot that prevented him from playing last Sunday against the 49ers.

"He's in the same situation," Nagy said. "He's going to want to try to do everything he can to get right and go out there. But there's no change with his status from, really, last week. We're just going to continue to keep working with him."

Mack also sustained his injury Oct. 3 in the victory over the Lions. He played in the next three games—registering 2.0 sacks—despite being either limited or held completely out of practice. But the Bears deactivated him against the 49ers, hoping it would accelerate the healing process.

Other Bears who did not practice Thursday were running back Damien Williams (knee), quarterback Nick Foles (personal reason), tight end J.P. Holtz (concussion), inside linebacker Alec Ogletree (ankle) and safety Eddie Jackson (hamstring).

Roster Moves: The Bears on Thursday made two practice squad moves, re-signing linebacker Sam Kamara and releasing receiver Jon'Vea Johnson.