A high temperature meant Nyquist did not head to Belmnt on MondayPICTURE: Getty Images
Nyquist in race against time to be fit for Belmont
USA: Nyquist, whose Triple Crown bid was ended when Exaggerator claimed the Preakness Stakes at Pimlico on Saturday, is a doubt for the Belmont Stakes after being found to have a high temperature on Monday.
The Kentucky Derby winner, who was previously undefeated, had a 102-degree temperature, according to the Daily Racing Form.
Nyquist did not ship to Belmont on Monday as had been planned on Monday, remaining instead at Pimlico, although O'Neill has not yet ruled out a run in the final leg of the Triple Crown on June 11.
Exaggerator team having fun
There are no such problems for Saturday's victory Exaggerator, a general 7-4 favourite for the Belmont with British bookmakers.
He had not beaten Nyquist in four previous tries but trainer Keith Desormeaux is looking forward to round six, should Nyquist make the line-up.
"Absolutely," he said. "This is fun, isn't it? There was no pressure on me; all the pressure was on Nyquist to keep the record perfect, so I totally enjoyed the day. Now that we've accomplished this, the pressure is even less."
Other Belmont contenders
The absence of Nyquist would leave a massive hole in what was shaping up as a cracking field for the Belmont.
Preakness runner-up Cherry Wine is a likely runner alongside his Dale Romans-trained stablemate Brody's Cause, well fancied for the Kentucky Derby before finishing seventh.
Preakness fifth Lani, the Japanese-trained UAE Derby victor, is also set to run again. Others coming back from the Kentucky Derby are headed by Suddenbreakingnews (fifth), Destin (sixth) and Mo Tom (eighth), which means that the Belmont could feature as many of seven of the first nine home at Churchill Downs on the first Saturday in May - if Nyquist makes the race.