The selection of Quinn isn't especially surprising considering Crennel at one point in time named him the starter. Matt Cassel will be the backup quarterback on Sunday.
As Danny Parkins of 610 Sports said today, this is the "least interesting" quarterback controversy in the NFL, which I can agree with. Cassel and Quinn aren't that much different from each other so picking Quinn doesn't change a whole lot with this game.
Quinn last started in Week 8 against the Raiders. He filled in for Cassel in the second half of last Sunday's game against the Bengals.
With Quinn now starting, one of the notable story lines is that he returns to face the Broncos, where he spent the 2010 and 2011 seasons.