American galloper Arrogate, rated the world's best horse according to Longines' rankings, has been beaten at the prohibitive odds of $1.10.
The Bob Baffert-trained grey was making his return to racing in the G2 San Diego Stakes (1710) at Del Mar and was expected to make short work of his four rivals.
Arrogate, a winner of seven of his eight starts leading into today's assignment, currently holds a rating of 134 - two points clear of superstar mare Winx.
Partnered by regular rider Mike Smith, Arrogate settled at the back of the small field and was spotting the second-last horse around three lengths at the halfway point of the race.
The $1.10-pop made some progress in the run to the final turn but faced an impossible task at the top of the straight and was eventually eased up to finish a distant fourth behind runaway winner Accelerate.
Trainer Bob Baffert was understandably stunned post-race and no doubt vets will cast an eye over the horse rated the best in the world.