"I just had [the surgery] to really go in there and look at what happened the last time, to see why stuff was still coming back or different things were still showing up," said Harris, referencing a 2008 procedure. "I went in, and it wasn't anything major, just some scar tissue and stuff from the other surgery. Now we are just playing it by ear. "
That somewhat contradicts the message sent by head coach Lovie Smith over the weekend. Smith told the media that Harris would practice on Monday, and he even declared the defensive tackle "100 percent" when the team reported to training camp on July 30.
"I wouldn't say [Harris has had a] setback," said Smith. "Soreness seeps in a little bit. That's all that happened as far as I see it.
"It's not like you've seen Tommie go down with an injury or anything like that. You practice this long, as hard as the defensive line is going, these things happen."
Harris has had very little participation in Bears training camp practices to date due to lingering injuries and he is getting impatient about it.
"The hardest thing is knowing how political this business is, and having to wear pads and sit on the sideline acting like I'm going out there and different stuff like that, but it's a bit frustrating," Harris said. "But I'm going to hang in there and just see how it plays out."
Harris finished second on the Bears in sacks with five in 2008. He missed two games last year due to knee soreness and rarely practiced during the week in the second half of the season due to the situation.
Harris has a history of knee and hamstring problems. He missed Super Bowl XLI and the NFC playoffs because of season-ending surgery to repair a torn left hamstring.
"Do I have confidence?" Harris shot back at reporters Monday when questioned about his faith in the left knee. "Yes, definitely, I have confidence in myself, in my knee. I've been playing on one leg and everything. I can play this game. It's a mentality. I'm just hanging in there man."
Smith wouldn't call the injuries a blow to team plans to have Harris back in the starting lineup by opening night at Green Bay.
Harris signed a four-year, $40 million contract extension before the 2008 season with an $18 million bonus, the highest ever paid to a defensive tackle at the time. He said he understands why the team is being cautious, even if he doesn't like the inactivity.
"I had surgery in March, so I didn't get a chance to do a lot of stuff that the teammates were doing," he said. "So they're far ahead of me. So I'm really just starting to catch up."
In other Bears news, linebacker Jamar Williams suffered a shoulder sprain and tight end Fontel Mines a knee sprain during Monday's practice. Cornerback Zack Bowman remained sidelined due to a pulled hamstring and Smith said he isn't close to returning at this point.
Jeff Dickerson covers the Chicago Bears for ESPNChicago.com. Information from The Associated Press was used in this report.