Mike Glennon was a really bad quarterback who had not shown enough to be given a shot at the top job in the NFL.
Fact:
Mike Glennon occupied the top job for a full season and in that season put up 2,608 yards with 19 TDs and only 9 INTs. That’s an almost 2:1 ratio which is decent even if it is not spectacular. The team replaced him with extremely talented rookie who would have pushed out a number of starting quarterbacks in the league. There was no shame in it. Over his three years, he managed to have a completion percentage of 59.