The error provoked howls of outrage throughout the Twitterverse and beyond.
Only, he wasn't the winner. A scoring error was later discovered. The bout was actually a majority draw. By that time, it was too late to bring the fighters back to the Octagon, depriving fans of what promised to be an epic fourth-round overtime.
With the year almost halfway done, that error that remains the clubhouse leader for 2012's judging blunder of the year. But as he prepares for a main-event rematch against McCall on June 8 at UFC on FX 3, the fighter known as "Mighty Mouse" has simply let bygones be bygones.
"I felt like it was a human error," Johnson told MMAFighting.com's Ariel Helwani. "I'm the type of guy who's not going to be like, ‘I'm pissed about this, I'm going to the athletic commission, blah blah blah.' My reaction to Dana [White] was, ‘what do you want to do about it?' Dana said we'd do a rematch, and I said, ‘alright, I'll be ready.' It was what it was, it was an entertaining fight and I'm ready to go do it again."
In the first fight, Johnson, who trains with Matt Hume at Seattle's AMC Pankration gym, Johnson won a decisive first round, did what most observers felt was enough to take round two, then undeniably ran out of steam in round three. McCall nearly finished Johnson, but the latter managed to hold on until the clock ran out.
In hindsight, the former bantamweight felt that mistakes made in dieting as he cut down to 125 for the first time led to a lack of energy in the fight's latter stages.
"The first time I fought Ian McCall I cut carbs completely out of my diet all through training camp," Johnson said. "I was afraid I wasn't going to make weight, that I'd get on the scale and it would be all ‘he weighs 128' and the people would throw cabbage at me.
"I basically cut all carbs on the diet, just eat chicken and greens all the time. When I rehydrated to fight Ian McCall, all I had was salad and chicken and water, but when you don't have carbs in your body, you're flushing all the water out of your body. ... You can tell MMA is a carb sport because its fast, its explosive, its not a fat storage sport."
While it's tough to recall fans an instance of fans throwing cabbage or any other form of produce at fighters during a weigh-in, Johnson isn't taking chances this time around.
"This time, I have carbs in my diet, I'm walking around at 140, eating whatever I want. I feel good."
As he gets ready for the rematch, Johnson says that he's focusing on himself instead of thinking about the fighter known as "Uncle Creepy."
"This time around I haven't been thinking about Ian McCall at all," he said. "Last time I thought about him all the time. Right now, I'm in a better place for some reason. I don't know why, maybe because my training camp's went so well so far. I'm ready to fight him again. I made a lot of changes to my diet and my training, which were what cause me to slow down, my gassing last time out. This time I feel really good and I can't wait to get in there."
That camp included a detour in Hawaii. Johnson married his wife, Destiny, on May 11. But the honeymoon was a working vacation.
"My wife is very supportive," Johnson said. "She knew I had a big fight coming up. We had already decided, if a fight falls on the marriage time, if I have a fight scheduled, we'll just train through it. We kind of got inspired by Mark Hominick when he got married when he was training to fight [Jose] Aldo. We went to Hawaii, it worked out pretty well. ... It's kind of hard to relax when you're in Hawaii, I'll be running the mountains, training for an hour and a half, then I'm out surfing. You're staying active the whole time."
One thing you won't see Johnson do between now and June 8 is lose focus by thinking about Joseph Benavidez, who will meet the winner of the Johnson-McCall rematch in the flyweight tournament final at a date to be determined.
"Who knows? I could beat Ian McCall and break my arm and my leg doing it, and then Ian would get the title shot because I'm injured. I can't let myself think that far ahead."