"We've been looking around at the quarterback position for a while," coach Lovie Smith said. " [We] had a chance to play against Todd a few times.
"Just felt it's a good addition to our team. [I] don't know if he'll play this week. As far as where he is on the depth chart and all those things, they'll work themselves out in time."
Collins, 38, played in three games for the Washington Redskins in 2009, and after rejecting an offer last week from the Bears, the veteran accepted a contract that includes guaranteed money in the "six-figure" range, according to a league source.
Interestingly, the team plans -- according to sources familiar with the situation -- to keep three quarterbacks, and open the season with Collins as the primary backup to Jay Cutler, at least initially, while moving current second-stringer Caleb Hanie to the No. 3 spot.
Sources indicated that offensive coordinator Mike Martz didn't feel comfortable opening the regular season with an inexperienced quarterback as the top backup.
"I'm out there to compete," Collins said. "I'm not gonna sell myself short. I've been the No. 2 guy for a long time. Ideally, you can step up and contribute just like the starter. So that's always been my goal throughout my career."
The club initially reached out to Collins, a 15-year veteran with just 20 starts on his dossier, in an attempt to add depth necessitated by a shoulder injury to Hanie in the preseason opener in San Diego.
Collins rejected the offer last week because it didn't include any guaranteed money.
Collins said he's somewhat familiar with Martz's system, after performing in similar schemes in the past with the Kansas City Chiefs from 1998-2005, and with the Redskins.
"I'm not sure yet really; I haven't discussed that," Collins said when asked if he'd be ready to play Saturday. "I still want to play, and believe I still can. I'm still healthy, and the other big thing [about joining the Bears] was the fit with this team, and specifically the offense. I don't think it should take too long. I think the core of the offense is the same. [Martz has] tweaked some stuff since I was in the offense a few years back, but the base of the offense and philosophy is the same. I don't really anticipate it being too long."
Hanie, meanwhile, hasn't been able to practice since suffering the shoulder injury. Sources familiar with the situation said his rehab has gone well, but the club will likely exercise caution with the quarterback in the coming days. There's a good chance he'll be held out of the preseason finale in Cleveland.
Hanie is expected to be fully healthy when the club opens at home on Sept. 2 against Detroit.
"It's always good to add competition; it'll keep you on your toes," Hanie said. "So I'm just gonna keep on doing the same thing I've been doing. I can't really control what their thoughts are. They try to do what's best for the team. So I've just got to worry about what I can control."
The Bears waived Eric Peterman to make room for Collins.
Michael C. Wright covers the Bears for ESPNChicago.com and ESPN 1000. ESPNChicago.com's Jeff Dickerson contributed to this report.