The Broncos quarterback was placed in a walking boot Wednesday and held out of practice after spraining his left foot in Denver's 30-27 overtime loss to Kansas City on Sunday night.
Siemian was injured on a sack by Tamba Hali just before Brandon McManus kicked a 44-yard field goal on the first possession of overtime. Siemian said his foot "felt kind of funny but wasn't too painful" and he stayed in the game, scrambling for 8 yards to kick-start Denver's next possession.
The foot was sore when he awoke Monday but has been improving. He said he was "a little sore today but nothing too crazy."
Coach Gary Kubiak indicated the injury wasn't too serious, terming his quarterback day to day.
Siemian demurred when asked if he was worried he'd miss the game Sunday at Jacksonville (2-9).
"I'm really not looking too far ahead," he said. "I really want to take it one day at a time, listen to (head athletic trainer Steve Antonopulos) and just put as much into each day getting better as I can. So, that's where I'm at now."
And the Broncos are facing the same scenario they did a year ago when Manning missed the stretch run with a left foot injury and Brock Osweiler went 5-2 in his place.
Manning regained his health and returned to rally the Broncos past San Diego in the regular-season finale, clinching the AFC's top playoff seed that proved so pivotal in their Super Bowl run that culminated with a 24-10 win over Carolina for the franchise's third title.
A month later, Manning retired a champion, Osweiler parlayed his play into a $72 million contract in Houston and Siemian, a seventh-round draft pick in 2015, eventually beat out first-round draft pick Paxton Lynch and veteran Mark Sanchez as Manning's successor.
The Broncos are in a more precarious position this time around.
Instead of chasing home-field advantage, they're scrambling just to get into the playoffs at 7-4 , two games behind Oakland and one behind Kansas City in their division.
Lynch lost his only start this season, 23-16 to Atlanta in Week 5, when Siemian was out with a severely sprained left shoulder, an injury that bothered him up until the bye last week when he was able to get rest and another cortisone injection.
Siemian had his best game Sunday night, throwing for a career-best 368 yards and three touchdowns without an interception and running for 23 yards with a long of 14.
He didn't want to contemplate being slowed down now just when he'd regained his health and mobility.
"I'm just taking it day by day and hoping tomorrow's better than today," Siemian said. "Today was better than yesterday, so that's encouraging."
He did say that he can play, "I don't think there's going to be any limitations on what I can do."
Kubiak said he trusts Siemian could play Sunday even if he misses practice all week like he did in Week 6 on a Thursday night against the Chargers.
The Broncos feel Lynch is better prepared to handle a spot start than he was two months ago if Siemian can't play.
"All the guys have a lot of trust in him," Siemian said. "It's kind of been exciting to see from the time he came into the building to where he's at now, how much he's grown. He's been doing a really good job."
Lynch said he's much more comfortable and confident now than he was when he was sacked six times and threw an interception in his starting debut on Oct. 9.
"I feel confident in me and I feel confident in the guys around me," Lynch said.
Kubiak also revealed rookie fullback Andy Janovich had season-ending surgery Tuesday on his left ankle. He was injured on the first play from scrimmage Sunday night but stayed in and played another 31 snaps.
Janovich had recently recovered from a broken right hand and brought a degree of toughness to an offence sorely missing one ever since bruising tailback C.J. Anderson had surgery on a torn meniscus in October.
"We'll miss him," Kubiak said, adding that converted tailback Juwan Thompson will assume lead-blocking duties along with tight end A.J. Derby. "When that kid was healthy and playing good it was a boost for our football team."
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