Mike Glennon could replace Josh McCown as the starter this season, even during training camp. That's a statement of fact, if only because I used the world 'could'. The question is: how likely is this scenario? We've seen some speculation that it's just a matter of time in recent weeks.
Former Houston Texans general manager Charley Casserly predicted that Mike Glennon would take over for Josh McCown before the season is over on NFL Network. The Tampa Tribune's Roy Cummings has repeatedly predicted the same thing, most recently on Bright House Sports Network opposite Jenna Laine.
I'm not entirely certain this is likely. Lovie Smith seems to completely trust Josh McCown, and see him as the team's leader. That leadership has been prominently on display this offseason. While there have been references to the fact that there's competition at quarterback, that has always come within the context of noting an overall philosophy of having competition at every position.
In addition, Lovie Smith has historically been reluctant to change quarterbacks during the season. It has happened, most notably when he benched Grossman in favor of one-time Buccaneer Brian Griese three weeks into the 2007 season, most in-season quarterback changes under Smith have been due to injury, not performance.
None of this means that Mike Glennon won't get a chance to start. If Josh McCown gets injured, obviously Glennon is going to take over. And if McCown is going to perform poorly in either training camp or the regular season, he could be replaced, too. But Lovie Smith's history and the public love for McCown suggest that that poor performance would have to be sustained and consistent before Glennon would get a chance to start.
I'm fairly optimistic on Josh McCown's chances this season. He performed admirably last season, and the offensive structure and supporting cast are similar to what he had in Chicago, and all indications are that he's having a very strong offseason. But there's also plenty of reason to be skeptical of his likely performance this season. And if you don't think he's going to be good, expecting Glennon to replace him is entirely reasonable.