Hagan saw action as a true freshman in 1988 in relief of Sal Aunese. Hagan thought he would be a backup in 1989, too, what was supposed to be Aunese's senior season.
Then, as Hagan said earlier this week, "everything changed."
Aunese was stricken with inoperable stomach cancer before the 1989 season.
"I was one of those young dudes who thought he knew it all," Hagan said of the months between his freshman and sophomore years. "When Sal got sick, everything just changed. Not just for me personally, but for our whole program."
The team dedicated its season to their sick teammate. Hagan was given the reins to the Colorado I-bone, an offense at which Aunese had become adept at running.
Hagan, it turned out, took it to another level.
The current CU running backs coach remembers a lively pre-game atmosphere as the team gathered to take on Texas at Folsom Field in the opening game of the '89 season.
"I remember leading up to it being nervous," he said. "Worried about not making a mistake. Having everything on my shoulders.
"Right before the game I remember Eric Bieniemy and a bunch of those guys just going crazy in the locker room. And then I started going crazy along with them.
"Then Coach Barnett pulled me aside and ripped me. He told me I had to be the most calm person on the field because I was the quarterback.
"I didn't listen to him, though," Hagan added with a chuckle.
"Having that fire in me, I went out and wasn't afraid to make a mistake anymore. I was playing out of the box. All the fear and all that stuff went away."
Hagan struck fear into the Texas Longhorns, instead. On the second play from scrimmage, Hagan ran 75 yards. But he didn't score.
He remembers it like it was yesterday.
"I remember getting caught at the 3 by Stanley Richards," he said. "I remember it was an option play to the left. The defensive end shot up the field for some reason, I have no idea why. I just cut up inside and raced down to the 2-yard line.
"Two plays later, Eric Bieniemy scored on 4 Wham – that was the name of the play."
Hagan ended the day with 116 rushing yards and 95 passing yards. CU won 27-6 en route to a 11-1 record. The next season, Hagan led the Buffs to the national championship.