Currently, there are no specifics on why he left the program.
Flacco, the brother of Baltimore Ravens quarterback Joe Flacco, had limited time with the Broncos in his freshman and sophomore seasons, being the backup to Zach Terrell. In two seasons, he completed 10 of 13 passes for 188 yards and one touchdown, while also being a threat in the running game, rushing 38 times for 340 yards and two touchdowns.
Flacco was in competition in camp to be the starting quarterback this season for the Broncos, and was one of the frontrunners, along with redshirt sophomores Jon Wassink and Alex Mussat.