The world's highest rated racehorse missed a place at 1/20 when Arrogate could finish only fourth in Saturday's Grade II San Diego Handicap at Del Mar.
Indeed, Accelerate won the 1m 1/16 furlong contest on dirt in the manner the stunned crowd expected Arrogate to score.
Accelerate led all the way and apart from being briefly pressed by Huerfano in the back straight was never seriously threatened and came home seven lengths clear at odds of 7/1 with Arrogate never a factor and beaten 15 1/4-lengths into fourth in the five-horse field.
Ironically Accelerate is the only horse to have beaten Arrogate, having defeated Arrogate by a neck at Los Alamitos when Arrogate was on debut.
Trainer John Sadler was as surprised as anyone.
"You want to win. You don't want to concede anything, but I'm surprised we won, because Arrogate is the best horse in the world," Sadler told the Blood Horse.
"A couple of things went right for us and one of them was Arrogate didn't fire his best. That's what has to happen for these big upsets."
Arrogate was racing for the first time since winning the Group I Dubai World Cup over 2000m at Meydan in March however, jockey Mike Smith could offer no excuses.
"I'm at a loss for words - He was just flat—so flat," Smith said.
"We were going around there OK, and then I took him outside like I did in the Dubai World Cup, but he just didn't pick it up,
"So I dropped him inside again and cut the corner, then wheeled him outside once more, and tried to get something from him. But he was just flat, he wasn't trying.
"So I just wrapped up on him and got him home safe. We've got to go back and start over again. Get it back right."
You can watch the race below.
