"I love Coach Pittman. He's a real good guy to just talk or be cool with. Butch Davis, he looks like a man with a plan. He looks like he's going to change the program totally around."
Mattes' relationship with Pittman – and primary recruiter Tommy Thigpen – began several months back.
"They text me and I call them up every once in awhile," said Mattes. "[Pittman] was saying he wants the best lineman in the state and right now he thinks I'm the best lineman in the state so he wants me at Carolina."
Before leaving Chapel Hill Sunday, Mattes made an addition to his list of scholarship offers.
"Basically, [Pittman] said ‘R.J., name all the schools that have offered you.' I named them and Coach Pittman was like ‘Well, you're forgetting one more.' I was like ‘What's that.' He said ‘Carolina.'"
In addition to UNC, Mattes holds offers from Clemson, East Carolina, N.C. State, Virginia, and Wake Forest.
"He's unique in that his size and his aggressiveness and his motor run constantly," said Bobby Cloninger, Concord (N.C.) Robinson's head football coach. "I think that's the biggest thing that has brought interest to him. He plays very hard, he's wide open, he's got great feet, he's got great hands, and he plays the game the way it's supposed to be played."
At the collegiate level, Mattes, a 6-foot-6 235-pounder, would best be suited for tackle, according to Cloninger.
"I think he's going to be an offensive tackle because of his height, his wingspan, his ability to move his feet, [and] he can play in open space on the edge and do a pretty good job," said Cloninger. "Depending on how much bigger he gets and how much speed he keeps will determine which side of the line [he'll play]. He's got exceptional feet right now for a kid his size. He's going to get stronger and with experience he could play that left tackle."
For Robinson, Mattes holds down that left tackle position as well as starting at defensive end.
Before visiting UNC, Mattes attended junior days in both Columbia and Raleigh.
"South Carolina, I went down there because they called me up the day before and told me to come down," said Mattes. "I didn't know they had interest in me until then. So I went down there, met up with my recruiting coach, got a tour of their football facilities and their stadium – their stadium there is nice, [and] got to meet Steve Spurrier. It was nice.
"I got to [N.C.] State at 11:30 [on Sunday] and left at 1:30. I sat and ate lunch with the coaches, [and] got to meet Tom O'Brien. I went upstairs in the Counselor's Suite and just sat down and talked to him individually about State."
Mattes has also unofficially visited Virginia and Wake Forest, and is planning a trip to Clemson during his spring break.
Over the summer, Mattes figures to hit the camping circuit hard.
"I'm going to hit like six camps this summer – just one-day camps," said Mattes. "I don't know, which ones yet, but I know I'm going to go to a bunch."
One-day camps at Clemson, North Carolina, and N.C. State are under strong consideration as possible destinations for Mattes.
Amid plenty of campus visits, Mattes has developed a soft list of favorites.
"Right now, basically my top three or four would probably be Clemson, Virginia, [North] Carolina, and [N.C.] State," said Mattes. "Of course, if I get other offers that's going to change my mind.
"With State, it's O'Brien. My dad played for him at Virginia – [O'Brien] was the o-line coach – and he's put a lot of offensive lineman in the NFL – that's my ultimate goal.
"With Carolina, Butch Davis has just impressed me with how he's going to change things up there.
"Virginia, I've always loved Virginia since I was a little kid with my Dad [playing there] and their staff up there is awesome.
"And Clemson, with the tradition and Coach [Billy] Napier is like one of the best coaches I've met."
Mattes said he could make a verbal commitment as early as the end of the summer, but might choose to wait until after his senior football season concludes.