"I'll tell you what, you can't be anything but excited," McCown said. "(Coach Lovie Smith) put that up there this morning about the oldest rivalry. To get to be a part of that in this atmosphere, I'm very excited. I'm very thankful. It's a great opportunity to go play and have fun; to play on Christmas and all that. Absolutely it's neat."
ESPNChicago.com reported Tuesday that McCown was being given the chance to win the starter's role in practice this week after Caleb Hanie had another disappointing performance Sunday in a 38-14 loss to the Seattle Seahawks. The Bears announced the switch Wednesday.
Hanie threw three interceptions -- two of which were returned for touchdowns -- extending the Bears' losing streak to four and pushing the 7-7 team to the brink of playoff elimination. Hanie has nine interceptions in the four games he's played since Jay Cutler broke his thumb.
McCown, who was acquired Nov. 23, replaced Hanie for the last two drives Sunday -- he completed one pass and threw an interception. Since 2007, McCown has attempted only eight passes, completing two.
"Other than just the excitement and the joy of being in between the stripes with the lights on again ... I think that first snap obviously will be exciting," McCown said. "But then after that, it's still -- and that's the cool thing about being in this locker room -- you have a job to do. That's to go play good football and help your team win.
"So I don't want to get too excited and too amped up. For me, absolutely it's a cool story and a cool moment. But at the same time, I'm a competitor. I want to win the game. I want to do right by the coaches and the other 52 guys in the locker room. So it'll be exciting for a little bit. But we've got to get down to business."
McCown addressed the challenge of learning Mike Martz's system in a hurry.
"It's not ideal for anybody in any offense," McCown said. "It's not ideal to come in this late. But at the same time, as a competitor you understand where the other guys are at. You've got to get yourself up to speed and ready to play.
"Everybody expects you just to go play and play well. That's the expectation for myself also; just to go out and do things to help us win the football game. If I keep looking back and saying, 'I only got here six weeks ago,' then it becomes an excuse [and] I think you leave an area for you not to play well because you're leaving something to fall back on. I'm trying to refuse to do that, and just say, 'You know what, you have to play well. The team's depending on you.' That's my stance."
Jeff Dickerson covers the Bears for ESPNChicago.com and ESPN 1000. ESPNChicago.com's Michael C. Wright contributed to this report.