An errant tee shot. Missed putts. An enduring image of the youngster from Northern Ireland slumped over his driver at the 13th hole.
Most people thought it might wreck him, but the lessons from that day and since paid off two months later with a record-shattering performance at the U.S. Open.
McIlroy shot 2-under 69 on Sunday at Congressional Country Club to win in dominating fashion. He eclipsed the records for total score with 268 and most under par at 16-under. Those numbers drew comparisons to Tiger Woods' record romp at the 2000 U.S. Open at Pebble Beach, and the only number McIlroy couldn't match was margin of victory. Woods won by 15, while McIlroy lapped the field at Congressional by eight.
"I felt like I got over the Masters pretty quickly," McIlroy said. "I kept telling you guys that and I don't know if you believed me or not. But here you go, nice to prove some people wrong."
McIlroy dominated Augusta National for 63 holes and came to the final nine holes with a one-shot lead. His tee shot at the 10th hole ricocheted left between two cabins, and he suffered a triple bogey.
A bogey at the 11th hole followed, and he made a double bogey at the 12th to effectively end his chances.
McIlroy took it all in stride. He shared a plane ride with winner Charl Schwartzel to a tournament in Malaysia and tried on the green jacket.
He had a talk with six-time Masters champion Jack Nicklaus, and most recently he completed a humanitarian trip to Haiti.
"I think the trip to Haiti put things in perspective for him," his agent, Chubby Chandler, said.
McIlroy seized control of the U.S. Open on Thursday and Friday. Under soft conditions thanks to rain throughout the week, McIlroy fired a bogey-free 65 in the first round. Then, he followed it up with 66 on Friday that included a double bogey on his final hole.
With people wondering if he would crack, McIlroy never did. He followed with 68 in the third round, and Sunday's 69 made him just the third player to shoot all four rounds in the 60s.
He also became the tournament's seventh wire-to-wire winner. At 22, he is the youngest player to win a major since Woods at the 1997 Masters and the youngest U.S. Open winner since Bobby Jones in 1923.
"What he is doing is very spectacular, and that's a little bit of history there, and it's always nice to watch it," said Schwartzel, who birdied the final four holes to win the Masters.
Australian Jason Day finished second, just as he did at the Masters, and a pair of unknown Americans, Robert Garrigus and Kevin Chappell, tied for third.
McIlroy's performance this week drew comparisons to Woods' dominant wins in the majors, and Padraig Harrington even suggested that McIlroy could break Nicklaus' all-time record of 18 major wins.
Woods sat out this tournament because of injuries to his left leg.
"When you win a major quite early in your career, everyone is going to draw comparisons, it's natural," McIlroy said. "It would just be nice obviously for him to be healthy again and get his knee and his Achilles in shape and be back out on the golf course, because he does bring a little something extra to tournaments. He's Tiger Woods. I'm just happy to be sitting here with the trophy that has his name on it."
Nicklaus has taken an interest in McIlroy's career since the young golfer sought him out for advice. At the Memorial Tournament two weeks ago, tournament host Nicklaus talked to McIlroy about his Masters meltdown.
"I really didn't give any advice," Nicklaus said during NBC's telecast. "I said I was sorry about what happened at the Masters, I hope you learned from it."
McIlroy apparently took the advice to heart.
"He's smart as a whip. He wants to learn, he wants to get better," Nicklaus said. "When you've got young people who want to do that, you take an interest in it."
For the first time since the inception of the Masters in 1934, no American has won in five consecutive majors. The streak started last summer with Northern Ireland's Graeme McDowell at the U.S. Open. South Africa's Louis Oosthuizen added the British Open, Germany's Martin Kaymer captured the PGA Championship and South Africa's Schwartzel triumphed in the Masters.