The long-haired teenager admitted that he didn't always feel as confident as he looked. He felt a bit of anxiety early on. But the first offensive play of the game, an 8-yard touchdown run by Joey DeMartino, helped settle him.
"That was really helpful actually, especially on the run," he said. "That was a great run by Joey, and that was great blocking by the offensive line, too. Once we got that, I thought we were going to roll."
Roll the Aggies did. Garretson wasn't out-of-this-world spectacular, but was sharp throughout the night. He had 144 yards on 15-for-23 passing with a touchdown. No picks.
Film study from the week before was painful, Garretson said, but necessary to move forward.
"There were sometimes you looked at it and said, 'Oh man, I wish I could've taken that back,'" he said. "But the best thing about it is I learned from it and plan on never making those mistakes."
Getting starter's reps in practice appeared to make an impact. Wells lauded Garretson on a strong week of practice, and DeMartino said he saw its effects.
"He just went out there and handled his business like he's done it before," he said of Garretson. "He prepared all week. And it showed."
The coaching staff simplified some things for Garretson, DeMartino said, but they expect to install more with two weeks to work with before getting Hawai'i at home.
But Saturday night wasn't all serious business for the freshman. One of the lighter moments came when he completed a pass to his fellow true freshman and roommate Wyatt Houston, which was Houston's first college reception. The two connected over the summer, and they'll look to connect more in the passing game to close out the season.
Houston wasn't the only personal connection Garretson enjoyed in Albuquerque - his family, including his parents, travelled out to see his first start.
"I had a bunch of family members coming down from Arizona," he said. "It was nice having them here."
If they keep coming, it might not be the last win they see from Garretson, either.
Kyle Goonkgoon@sltrib.comTwitter: @kylegoon