Gronkowski will not travel to America for the Kentucky Derby at Churchill Downs after spiking a temperature.
The Jeremy Noseda -trained colt is named after New England Patriots tight end Rob Gronkowski, who last week acquired a share in the horse in anticipation of watching him in the 'Run for the Roses' on Saturday week.
But those dreams are now over as the son of Australian stallion Lonhro, who is unbeaten in four starts, suffered a setback.
Owners Phoenix Thoroughbreds made the announcement on Twitter.
"We very much regret that #Gronkowski will miss the @KentuckyDerby after spiking a fever over the weekend and being treated with antibiotics. "He can't make the long journey to Louisville but is doing well," Phoenix said.