Perhaps it's because his poor judgment kept him sidelined for a year.
As a high school senior, he was listed as the nation's top running back by both Rivals.com and 247sports.com, and he scored a touchdown in the Army All-American game. Fans who watched his highlights hailed him as the next Adrian Peterson, the last back with similar hype who chose to become a Sooner. But last July, he punched a woman in the face at a restaurant and was suspended for the season.
Mixon is back, and now that his teammates and coaches have had a chance to see him, the buzz is back, too - but for more than just his talent. Offensive coordinator Lincoln Riley said Mixon has emerged as a leader, despite being just a redshirt freshman.
''We threw a long touchdown pass today where we were on the 10-yard line,'' Riley said. ''It went all the way the other way, and it's hot out here, we're right in the middle of two-a-days, and he sprints all the way down there and chest bumps with that guy. And he does that every time that we score. His energy and passion for playing, and really just for life, is pretty infectious out here.''
Of course, his ability stands out, too. He's a 6-foot-2, 217-pound athletic freak with breakaway speed.
''Very elusive,'' said Samaje Perine, an All-Big 12 running back last season. ''He's going to be tough to stop. He can make moves in tight spaces. It's great to watch.''
It appears Mixon will be ready to contribute when he makes his college debut Sept. 5, at home against Akron. Coach Bob Stoops said Mixon performed well at last Saturday's scrimmage.
''Joe looked really good,'' Stoops said. ''He's had a great camp. He's run the ball well, rarely misses a hole. He's been fast and decisive with his cuts. Catching the ball great. All of it's been really positive.''
Quarterback Trevor Knight smiled when recalling a play Mixon made in a recent practice.
''He was split out the other day on a fade ball down the sideline, and he went up, really, into double coverage and brought it down with one hand.''
Offensive line coach Bill Bedenbaugh said he doesn't recall seeing a player with Mixon's versatility.
''I don't know that there are many guys in the country like him,'' Bedenbaugh said. ''His skill set for his size is impressive.''
No matter how well Mixon performs, he carries his past with him. Stoops said the staff does its best to help players avoid such incidents. At the start of the summer, the staff had the players attend five days of seminars in hopes of giving them tools to deal with challenges.
''You do your best to educate early, and you want to continue to build them as young men that, you know, realize where you are,'' Stoops said. ''This is a college campus. Some might have been on a mean street somewhere, and that isn't the case anymore. You've got to learn to adapt to your new environment.''
Mixon is making the most of his second chance so far, and people around the program say there's much to look forward to if he stays out of trouble.
''I think the physical talent and the plays that he's going to make will speak for themselves,'' offensive lineman Ty Darlington said. ''We'll all see it on Saturdays. He's going to be pretty special.''
Follow Cliff Brunt on Twitter: www.twitter.com/CliffBruntAP