The 6-0, 190-pound Barnett has taken advantage of an opportunity placed before him this fall. Sophomore Orhian Johnson was pegged to take over the starting position vacated by Kurt Coleman, but he suffered a leg injury during camp that gave Barnett the opportunity to overtake him.
The graduate of Clayton (Ohio) Northmont – which also happens to be Coleman's alma mater – seized the opportunity.
"Orhian got hurt a little bit so C.J. stepped in," safeties coach Paul Haynes said. "You talk about a guy who exceeded expectations a little bit, it's him because I didn't know if he would step in there and take the role that he did. He's very athletic. He's a very smart kid. He can handle it mentally.
"Plus, I don't know if it's in the water at Northmont or not but he's a very calm kid who doesn't crack under pressure. It's been a smooth adjustment for him."
Head coach Jim Tressel said it was a combination of playing well and Johnson's injury that helped Barnett ascend to the role of starter.
"Just like anything else, you get opportunities and you have a chance to get more reps and things like that and you impress," he said. "C. J. has been very impressive. That doesn't mean Ohrian is not in the thick of a battle. But like anything else, if one guy is in there doing the work and he's getting better and the other guy unfortunately misses (practices), it makes it more difficult."
Tressel said Johnson missed about a dozen practices during camp. The 6-2, 205-pound native of Gulfport, Fla., entered OSU as a three-star quarterback prospect who projected as a defensive back.
As a senior, Barnett was a four-star prospect and ranked the No. 14 cornerback nationally by Scout.com. He recorded 65 tackles and deflected 13 passes that season before graduating early and enrolling for spring practice.
As a freshman, he recorded four tackles while seeing action in eight games primarily on special teams. In his first career start, Barnett recorded two tackles against Marshall.
This past spring was his first full practice session at safety, he said.
"It was really good because I came here at corner and went through the first camp and the first spring at corner, so this spring and right now I'm all at safety," Barnett said during camp. "It's a lot easier for me to learn it right now starting fresh instead of having to learn it during the season and learning as I go."
The biggest adjustment to playing safety, he said, has been grasping the bigger picture on defense.
"It's tough because playing corner in high school I really didn't have to learn football as much as playing safety (where) you have to know everything," he said. "When you're playing corner you have to know what some people are doing but really you can get by just knowing what you need to do. Playing safety, you have to have a good concept of the whole defense."
Along with the rest of the OSU defense, Barnett figures to be tested Saturday by Miami (Fla.). Haynes said the Buckeyes expect the Hurricanes to try to use a power running game to set up the play-action pass.
That means the play of the safety duo of senior Jermale Hines and Barnett will be key. Haynes said his last words of wisdom to Barnett will be about having good eye control.
"Just (read) your keys," the coach said. "If you sit there and have your eyes in the backfield and trying to stare at certain things that you're not supposed to, that's what gets you in trouble. Every down, you've got to have great eye control and great eye discipline on what you're actually supposed to be looking at."
Barnett clearly values his role on the OSU defense. His left arm is adorned by a tattoo with the words "Silver Bullets" emblazoned on his forearm.
"I got (it) this past winter," he said. "It's just something that the defense holds true and dear to us. We'll keep it in the family."