The Broncos' rookie is throwing the football without pain. He is one of 4 players on IR eligible to return at midseason, although team can only bring back 2.

ENGLEWOOD, Colo. — Through the lonely existence that is injury rehab, Drew Lock is coming along fine.

The tough part isn’t necessarily the physical grind of recovering from the injury on his right passing thumb. It’s the mental challenge of dealing with the boredom of it all. Is Lock, a Broncos' second-round rookie quarterback, going stir crazy?

“A little bit, yeah,’’ he said. “Been doing the same thing for 9-plus weeks. I’ve never had an injury that kept me out of football till now. I’d rather be out there practicing with everybody but I knew going into it, it was going to be like this.’’

Lock is throwing the football again. He can’t practice with the team while he’s on injured reserve but he can throw all he wants on his own.

“It feels great,” he said.

The thumb?

“Slowly working back,” he said.

Is there pain?

“No, not when I’m throwing or grabbing things,’’ Lock said. “Now, if you were to smack it, yeah, it’d probably still hurt.”

Lock can start practicing with the team the Monday after the Broncos play the Tennessee Titans next Sunday at Empower Field at Mile High. He would then be eligible to become activated on the Broncos’ 53-man roster in time for the team’s week 9 game at Indianapolis.

But there’s a catch. Besides Lock, the Broncos have two other players -- running back Theo Riddick, tight end Jake Butt – who are also eligible to be activated in week 9. And a fourth player on IR, receiver Tim Patrick, is eligible to return for the week 11 at Minnesota.

Only two of those four can be activated; the other two would stay on IR for the rest of the season.

The next four games will help determine whether the Broncos want to activate Lock as a backup to starting quarterback Joe Flacco, or use those two roster spots on players who can more immediately contribute on game day.

‘I think I’m going to wait to see what the team does first, before I say anything,’’ Lock said. “Obviously, whatever they decide I’m going to back them on.”

In the meantime, does Lock get anxious when he sees Jacksonville rookie quarterback Gardner Minshew II – who was drafted four rounds after Lock – have so much early success?

“No, no,’’ Lock said. “I’m happy for Gardner. When you see a guy out there who’s our age and he’s playing the way he is, it proves the young guys can play. He helps us out.”