Nyquist -- 'Plan Is to Run Belmont' ... Will Recover From Fever

Nyquist -- the winner of the Kentucky Derby -- is still battling a fever ... but his team believes he'll beat the illness and WILL compete at the Belmont Stakes next month.

We spoke with Nyquist's assistant trainer, Jack Sisterson, who tells us the champion thoroughbred still has an elevated temperature, as he did following the Preakness, but the team believes it's not that serious.

"Nyquist is going to be fine," Sisterson tells us ... "The plan is to run in the Belmont [on June 11th]."

"These fevers happen sometimes, but not often."