But on Saturday night at UFC 128, it was Rua who looked like the inexperienced fighter. Jones beat him more easily than almost anyone could have imagined.
But one person saw it coming: Jones' mother, Camille.
"I saw this coming," Camille Jones told ESPN.com. "This fight, I was the most relaxed that I've ever been.
"I was so sure that he was going to win, and that he was going to do an excellent job. The only thing that I was wrong about, I thought that Jon was going to do it in the first round."
Jones was bigger, quicker, stronger and more confident. With so many elements in his favor, Jones didn't need the allotted five rounds -- he finished Rua at 2 minutes, 37 seconds of the third round.
Before he entered the cage at Prudential Center, Rua had a look of uncertainty on his face. He'd seen enough video of Jones to know that none of his former opponents had prepared him for Jones. As good as Jones might have looked on those tapes, he was much better Saturday night when the horn sounded. At no point in the fight did Rua appear on the verge of challenging the young challenger.
But this fight wasn't just about Rua's inability to mount any type of attack. This fight quickly became about Jones, just how good he is and how good he will become.
"With what I saw tonight, it looks like he is a mile and half ahead of everybody else," UFC president Dana White told ESPN.com. "He looks incredible.
"In my opinion, not only is he the No. 1 light heavyweight in the world, he just shot up in the pound-for-pound category as well. What he did tonight was phenomenal. I don't know what else to say."
Jones' reach, which he uses to perfection, kept him from harm's way. His quickness allowed him to escape any potential problems.
Then there is his confidence. There was never a doubt in Jones' mind that he would take Rua's crown and become the youngest champion (23 years old) in the UFC.
As good as he was against Rua, Jones is nowhere near his peak. He is still an MMA infant.
This fight proved that Jones is still a work in progress. He has been getting better with each fight, and that spells doom for any 205-pound fighter.
"I'm getting closer to becoming really, really, really good," Jones told ESPN.com. "The biggest difference is that I'm more comfortable going for it. Once you get that out [of] the way, all the tricks can come out.
"I'm really excited. When I become really, really good, that's when the fun starts."
Jones isn't the first light heavyweight in recent years to be proclaimed unbeatable. Lyoto Machida hadn't lost a round in the UFC by the time he won the belt from then-champion Rashad Evans. Machida had a style no one in the UFC light heavyweight division had figured out. But Rua was familiar with Machida's fighting style; the two had sparred briefly in the past.
Jones is different, however. It's not simply his unorthodox style, but his supreme athleticism. Jones is a super athlete and it seems to run in the family. His older brother, Arthur III, plays defensive end for the Baltimore Ravens; his younger brother Chandler is a star defensive end at Syracuse University.
There seems to be no formula for overcoming Jones' unique skills, unless a fighter has had a training partner with similar abilities.
Jones' next opponent, Rashad Evans, is in the fortunate position of having had a training partner with that skill set: He's actually trained with Jones. Evans is more familiar with many of Jones' tendencies than any other light heavyweight. At this moment, he has the best chance of upsetting Jones.
No date has been set for that showdown, but if Evans can't handle Jones, no one else will be in position to do so in the foreseeable future.
But when the two are scheduled to fight, then Jones might face his stiffest test ever. It's not that he must offset Evans' familiarity; Jones and Evans share many of the same trainers. Those trainers must decide which fighter they will have to part with.
Being in that position made it difficult for them to fully enjoy Jones' title win.
"This is bittersweet for me," Muay Thai coach Phil Nurse told ESPN.com.
Franklin McNeil covers MMA and boxing for ESPN.com. He also appears regularly on "MMA Live," which airs on ESPN2. Follow him on Twitter at http://twitter.com/Franklin_McNeil.