And in his last — near-perfect — 100-meter hurdles race of the year, the American put in a world record-breaking performance that had him shaking his head in disbelief.
Merritt finished in 12.80 seconds Friday at the Van Damme Memorial, slicing a full 0.07 seconds off the 4-year-old world record set by Cuba's Dayron Robles.
In an event where records are usually broken by one or two hundredths at a time, Merritt was as stunned as the crowd when his time came up.
"It was, 'What? What? What is this I am seeing?" he said. "I just started screaming because I was in complete shock because I could not believe I could run that fast."
It was by far the marquee moment of the final Diamond League meet of the season, totally upstaging Usain Bolt's routine 100 victory in 9.86.
Merritt shot out of the blocks and didn't touch any of the 10 hurdles he swept over. Sensing the moment had come, he lunged at the line with both arms flung backward and chest outward.
The American already had the six top times of the season and had come within 0.05 seconds of Robles' mark. But in balmy conditions with a slight tail wind, he finally shattered the record.
"It was almost perfect," Merritt said. "I knew the track was going to be scorching."
So was he.
Merritt dominated this entire season while stars like Liu Xiang and Robles struggled to keep up and then both pulled up injured at the London Olympics.
He knew he was in striking distance of the world record, clocking 12.93 in three races and winning the Olympic final in 12.92.
"I knew one day (I'd break the record), I didn't know when," he said. "It was kind of getting frustrating, because I kept running the same time over and over."
He had hoped to break it in Lausanne on Aug. 23, but he was so pumped with adrenaline that he false-started.
He came to Brussels early, felt the track under his feet, and had the same feeling as at the London Games.
His goal was to clock 12.85, because in hurdles, records usually get beaten by tiny margins. Even his phone password was 1285.
Time to change it to 1280.
"I was in shock when I saw the time pop up on the scoreboard," he said.
It was the biggest improvement of the record in 31 years.
Jason Richardson was second, way behind in 13.05.
Bolt, for once, was almost an afterthought. The triple Olympic champion ran a controlled race after a slow start to win the 100 and win the diamond trophy for the top competitor of the season.
"I want to take it easy now," Bolt said.
Fellow Jamaican sprinter Yohan Blake followed it up with a blistering 200, blasting out fast from the gun before finishing in 19.54 seconds, unchallenged by anyone.
Merritt was equally dominating. Now his only problem is getting home on Saturday to the United States so he can start properly celebrating his Olympic triumph and world record.
After shaving a massive 0.12 seconds off his personal best, his whole body was aching.
"I need some treatment," he pleaded, "so I will be able to walk onto the plane."