Both were 16. MacDonald wouldn't turn 17 for another five weeks. Mein had another four months to go.
It was Mein's first pro MMA fight and MacDonald's third.
MacDonald — then fighting out of Kelowna, B.C. — won their encounter at Rumble in the Cage 17, a home-town show put on by Mein's father Lee, by rear-naked choke at four minutes four seconds of the first round.
"I remember being very disappointed, (having) let down all my friends and family," recalled Jordan Mein.
"And it was embarrassing," he added with a laugh.
MacDonald, understandably, has a slightly rosier memory.
"It was a good fight for me," said the Montreal-based 170-pounder. "Jordan's a very tough character and I kind of expected after the fight that we would meet up later in the UFC later in our careers."
That could happen.
Both currently campaign in the UFC, with Mein fighting Matt (The Immortal) Brown on Saturday in San Jose and MacDonald meeting Jake (The Juggernaut) Ellenberger on July 27 in Seattle. Both are televised cards.
The two fighters are now 23, but old beyond their years in fighting terms.
On the UFC's official website, Mein lists his job before fighting as "making it to class in high school."
MacDonald offered a few more details in his response.
"Labouring jobs for the most part. I jumped from job to job a lot of the time because I hate work. Basically I only like fighting."
Both are cool as can be in the cage.
Mein (27-8) is coming off an impressive showing in his UFC debut in March, when he knocked out veteran Dan Miller in the first round at UFC 158 in Montreal.
Before that he went 2-1 in Strikeforce. A split decision loss to Tyron Woodley on a Strikeforce card in January 2012 is Mein's only setback in his last 10 fights.
MacDonald (14-1) has won four straight since losing to Carlos (The Natural Born Killer) Condit at UFC 115 in June 2010. While injuries have slowed his charge in recent months, his last outing was a lopsided decision over former champion B.J. Penn in December.
The UFC rankings have MacDonald at No. 3, behind Condit, No. 1 contender Johny Hendricks, and champion Georges St-Pierre. Ellenberger is ranked No. 4.
MacDonald, whose overall UFC record is 5-1, was slated to meet Condit in a rematch at UFC 158 but had to pull out after spraining his neck in training.
That forced a reshuffle of the card. Hendricks went on to win a decision over Condit while Ellenberger knocked out former Strikeforce champion Nate (The Great) Marquardt in the first round.
Mein (pronounced MEE-in) hopes he gets to meet MacDonald again.
"Absolutely. I'm doing my best to keep my career on path and to keep winning. And he's doing that as well. So I'm sure they will line up eventually."
Said MacDonald: "You never know what happens. Right now I'm just thinking about Jake. If I can continue to win and Jordan continues to win, then maybe it will get set up. But it's really just a matter of how things continue to roll. I'm not really in charge of that."
Mein also has more pressing matters on his mind, having stepped in for Dan (The Outlaw) Hardy against Brown in San Jose.
Brown (16-11) has reeled off four wins in a row after going 1-4 in his five previous UFC fights. His most recent victim was Mike (Quick) Swick, whom he knocked out in the second round in December.
"It's a dangerous fight," Mein said cheerfully. "Get a good win here and it will be nothing but good for my career."
Mein agreed to replace Hardy less than a week after his win over Miller.
Mein's philosophy has always been "if you're healthy, you should definitely step in there and challenge yourself and take short-notice fights."
And fortuitously he had decided to change up his training regimen after the Miller win. Rather than take a few weeks off, he elected to go straight back to the gym.
Days later he got the call to fight Brown.
"We jumped at it," Mein said.
A fight fan as well as a fighter, Mein watches a lot of MMA. He can also be found in front of a video game console, playing at being a UFC fighter.
He is an unabashed fan of Brown, calling the matchup a "dream come true."
"He's very gritty and stays in everybody's face. And always puts on an exciting fight because he's just willing to try and hurt you the entire time," said Mein.