The Steelers sustained numerous major injuries at the end of last season, have a lengthy PUP list, nasty-looking injuries in preseason games and one very prominent and lengthy holdout.

Yet here they are, five days before the season opener, and coach Mike Tomlin has only ruled out two players for injury-related reasons for the Sunday night game at Denver.

Rookie G David DeCastro (knee) and reserve LB Stevenson Sylvester (knee) will not play against the Broncos, Tomlin said Tuesday. Tomlin also said starting FS Ryan Clark will be held out of the game, as expected, because he has the sickle cell trait in his blood that is exacerbated by high altitude.

Tomlin wouldn't rule out LB James Harrison (knee), LB Jason Worilds (wrist), RB Rashard Mendenhall (knee) and RB Isaac Redman (ankle) after each of them made it through practice -- to varying degrees -- Monday.

"Some of those guys... are closer to returning than others, but we are going to monitor their progress and make the decision as we push forward through the week," Tomlin said. "We will base our determination on how they respond to the work."

It would be shocking if Mendenhall played. He is recovering from tearing his right ACL in the regular season finale Jan. 1 in Cleveland, came off the PUP list late in camp and did not appear in any preseason games.

Of course, neither have Worilds and Harrison, who were eligible to practice for the first time Monday. The Pittsburgh Post-Gazette tweeted that Harrison gave a thumbs-up when asked how his knee responded to the workout 24 hours later.

Specifically speaking about Harrison, Tomlin said, "The issue is just whether or not he gets a clean bill of health from our medical staff. He has to this point in terms of being able to practice. We'll see how his body responds to that work and let that be a determinant about how we move forward."

Redman was anointed the starter in Mendenhall's stead but has had an injury-riddled preseason that included a groin/hip injury before the ankle ailment. He did not practice Monday.

Dwyer on Tomlin's good side: If Redman is limited, expect to see more of RB Jonathan Dwyer. Dwyer reported to camp in better shape than he had in his previous two seasons and has been virtually the only Steelers running back to avoid any question of health over the past six weeks.

"He's a young man that I believe is maturing," Tomlin said. "There's a certain level of growth and maturity from a personal standpoint. The more obvious observation is that he is in better physical condition than he has been in the past."

Hampton no longer a concern? Throughout training camp, even as he wasn't practicing and even as another injury (left elbow) crept up, NT Casey Hampton assured anyone that would listen that he would be fine.

Less than eight months after tearing the ACL in his left knee, apparently Hampton is.

"He participated, and he participated in an above-the-line fashion in the last preseason game," Tomlin said in response to why Hampton wasn't listed among his injured players. "We haven't looked back with Casey."

Wallace's first practice "pretty productive": Tomlin was pleased with how WR Mike Wallace looked Monday in his first practice since ending his holdout last week.

"I was generally positively impressed with his general, overall understanding of what it is he needs to do," Tomlin said. "No. 2, I think he displayed a decent level of overall physical conditioning. Obviously, that practice setting and that limited practice setting is not football games; it is not a hostile environment, it's not NFL stadiums, so we'll temper that excitement."

When asked if Wallace has a chance to start Sunday, Tomlin said, "I didn't see anything yesterday that would lead me to believe that's not a possibility."

Lewis, Allen both draw praise from Tomlin: Tomlin refused to come out and say it, but CB Keenan Lewis earned the starting spot vacated by William Gay's departure via free agency. But Lewis' primary competition for the job, CB Cortez Allen, also showed he was capable of handling the duty.

In today's NFL, both players will play extensively. Tomlin had kind words to say about the development of both the fourth-year Lewis and the second-year Allen.

Tomlin said Lewis looks the best he's seen him. "He's done a nice job here in this preseason in working and playing good, sound, technical football," Tomlin said.

Tomlin said Allen "has grown by leaps and bounds."

Makin' it Rainey on returns: Tomlin confirmed what the team's official depth chart told us about RB Chris Rainey -- that he is the Steelers' primary punt and kick retainer.

Follow Steelers reporter Chris Adamski on Twitter @CBSSportsNFLPIT and @BuzzsawPGH.