The UFC is one of the fight promotions that generally does it correctly when moving its fighters, rewarding those who score big wins by pushing them closer to title contention.
In just his second UFC fight, though, MacDonald became one of the sport's hottest names, despite a loss to Carlos Condit.
The match seemed odd at the time. Condit was a veteran who held the World Extreme Cagefighting welterweight title and had won nine of his past 10 against elite competition.
MacDonald was just 20 with only one UFC fight and no bouts with anyone near Condit's level.
But MacDonald justified the faith that UFC matchmaker Joe Silva showed in him, putting on a Fight of the Night battle with Condit that the veteran narrowly pulled out by coming on down the stretch.
The reaction, though, was awe: Awe that a 20-year-old could perform so well under such difficult circumstances. Awe that MacDonald showed the full arsenal of weapons. Awe that he was even in the fight.
That led to MacDonald being viewed as the UFC's most promising title prospect.
A little more than three years later, nothing has changed. MacDonald is still a prospect, still hasn't beaten a Top 10 competitor and still is inspiring talk of greatness from those who have watched him fight.
On Saturday, though, MacDonald will, finally, get a chance to justify the talk. He'll meet tough Jake Ellenberger in the co-main event of UFC on Fox 8 at Key Arena in Seattle, the same venue where, in December, he destroyed one of the UFC's legendary fighters: B.J. Penn.
MacDonald has answered countless questions from fans and media in the three-plus years since that Condit fight about his good friend and training partner, UFC welterweight champion Georges St-Pierre.
If he beats Ellenberger on Saturday, he'll finally justify some of the talk.
[Related: UFC on Fox 8: Contender John Moraga's title quest forged by tragedy]
Prospects bust all the time. Ask Yankee fans about the can't-miss pitcher Brien Taylor. Or ask Chargers fans about can't-miss quarterback Ryan Leaf.
MacDonald has proven to be anything but a bust since the Condit fight, but he's also not moved as quickly as might have been expected. Since losing to Condit, he's beaten Nate Diaz, Mike Pyle, Che Mills and Penn.
Diaz and Penn were blown-up lightweights who shouldn't have been fighting at welterweight. Mills isn't good enough to compete at a high level in the UFC, while Pyle is a solid veteran without a defining victory.
Ellenberger would be exactly that for MacDonald. Ellenberger is 29-6, has won eight of his last nine and has beaten the likes of Pyle, Jake Shields, Nate Marquardt and Diego Sanchez along the way.
"This [would be] a huge win for [MacDonald], not to mention the fact that Ellenberger's last win was very impressive, and yes, this is definitely his biggest [test]," UFC president Dana White said. "It's not only his biggest fight, but it's his biggest test."
MacDonald has been haunted by questions about St-Pierre since not long after he lost that 2010 bout to Condit. It was understandable, in a way, because MacDonald showed the kind of all-around game that would seem to make him a threat to the champion.
That talk, though, was always projecting and the low-key MacDonald wasn't much for it. He didn't want to talk about St-Pierre, even if he was hounded on the topic. But if he beats Ellenberger on Saturday, he'd likely be in position to fight the winner of the UFC 167 main event between St-Pierre and Johny Hendricks.
MacDonald, though, wouldn't even consider questions about the topic, keeping his thoughts solely on Ellenberger. He wouldn't rule out a move to middleweight so he wouldn't have to fight St-Pierre, but he also wouldn't rule out staying at welterweight and taking on the St-Pierre-Hendricks winner.
"I'm just going to focus on this fight [against Ellenberger] for now," MacDonald said. "My whole career has just kind of been going with the flow. Everything changes after each fight, so I'll see where I am after this fight, and it's just [up to me to evaluate] the options from there. Nothing's out of the question."
What will be out of the question will be talk about a fight with St-Pierre if MacDonald were to lose. When he was 20 and new to the UFC, he could benefit from a loss to a highly ranked veteran.
Now, it's all about winning for MacDonald. Ellenberger has had to take the hard road up, and now that he's nearing the top, he's having fun with the journey.
He's poked fun at MacDonald on his Twitter feed and he's been outlandish in interviews. It's likely he's trying to throw MacDonald off, but MacDonald can't afford to be distracted by words.
"I haven't said anything that isn't true," Ellenberger said. "And my message to Rory is pretty clear: For him to start tasting some flavors of baby food and find which ones he likes and stock up, because this isn't the Tears for Fears lookalike contest. All I said to him was prepare for some horizontal television time, and I meant it."
MacDonald chose not to respond and said he's not worried about trash talk. He needs to be concerned about performing.
Because if he beats Ellenberger, it may be that, finally, a star is born.
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