Simms is in line to make his first start since September 2006, when he suffered a life-threatening spleen injury while with the Tampa Bay Buccaneers.
Listed as questionable, Orton will be put through a workout before Sunday's game, and how he performs will determine whether he plays, Broncos coach Josh McDaniels said Friday.
"If Kyle is completely able to do what we're going to ask him to do in the game plan, and can do it at a level that allows us to be successful, then we could give him an opportunity to play," McDaniels said. "If he's not capable of playing at that level, or doing some of the things that we need him to be able to do, then you go with the guy who practiced."
McDaniels said Orton "absolutely" still has a chance to start, though he conceded playing him without the benefit of any practice during the week was much less than ideal.
In a somewhat similar scenario a week ago, Simms was thrust into the lineup in relief of the injured Orton with little or no preparation. The backup had a rough go, completing 3 of 13 passes for 13 yards with an interception. In the case of Simms, though, it was his first significant action since he underwent emergency surgery more than three years ago to remove a ruptured spleen.
Simms said Friday that he was approaching the game against the Chargers as if he would start and he felt better prepared to play at a high level after a week's worth of practice.
"If needed, I'll be ready," Simms said. "I know I haven't had a great deal of playing time the last few years, but I think a lot of guys saw what I did in training camp and the snaps I got in the preseason, and hopefully they are as confident in me as I am in myself."
McDaniels said he and the rest of the team have a great deal of faith in Simms, who worked through a long, difficult rehabilitation to restore his health to where he could play again.
"I think it's hard not to have a great deal of respect and appreciation for what he's been able to overcome," McDaniels said. "We have a lot of confidence in him, and I know the coaching staff does and the players have practiced that way this week. We expect to play well if he's playing. I think the team feels the same way about him, and we'll embrace that situation if that's what we're doing."
Tight end Daniel Graham said it's not like he and his Broncos teammates are starting from scratch with Simms because they had a chance to extensively work with him during training camp. That has allowed them to quickly make adjustments to Simms' style this week, including catching balls with the differing spin from a left-handed quarterback.
"We've had a good week of practice with Chris in there," Graham said. "He's been doing a good job of leading this team and continuing where Kyle left off. We've all had the chance to catch balls from Chris this week, and if he gets to go on Sunday, we'll all be ready."
For his part, Simms would like nothing better than to put an exclamation point on his comeback.
"I've been through a lot," he said. "I've always loved the game of football a great deal, and to have it almost taken away from me, and then to be back kind of in the mix of things, it's a special time for me and my whole family. I'm excited."
Copyright 2009 by The Associated Press