No boots allowed.

Not while the Denver Broncos practice they aren't. Thus, quarterback Trevor Siemian was not present. Siemian is battling a left foot sprain that may force him to miss the Broncos' game this Sunday at Jacksonville.

“He’s still in the boot,'' Kubiak said. "He’s feeling better today, but it was the same process today as it was yesterday.”

If Siemian can't play -- and that's the way to bet -- the Broncos will start rookie Paxton Lynch with veteran Austin Davis serving as the backup. Lynch and Davis were the Broncos' quarterbacks during practice Thursday.

Also not practicing were center Matt Paradis because of his two bum hips, and receiver Bennie Fowler, who has a knee injury.

Lynch started one previous game, a 23-16 loss to Atlanta.

“I would tell you from a coaching perspective, it’s more us seeing what he handled that day,'' Kubiak said. "What he could do—his comfort level. That’s what we have to look at. I’m sure he would probably go from an experience standpoint, the speed of the game and on game day being the starter, and also the night before the game being the starter with the team. Those are things that are a little bit different than showing up knowing you’re the backup on any given day.”

He also came off the bench in a win at Tampa Bay.

For the season, Lynch has completed37 of 59 passes for 393 yards, two touchdowns and one interception for an 86.3 passer rating. Siemian has an 89.2 rating.