One-time Melbourne Cup favourite Kings Will Dream is being closely monitored after suffering a pelvic fracture and ruptured blood vessel in the Cox Plate.

John Allen pulled the Darren Weir-trained Kings Will Dream out of Saturday's race won by Winx and the gelding was taken to the Ballarat Veterinary Clinic.

Managing owner Brad Spicer said on Twitter the next three days would be critical.

"He sustained a pelvic fracture & ruptured a blood vessel which thankfully looks to have clotted over night. The next 24- 72 hours is critical as he will be monitored closely, the vets are still concerned the blood clot can be disturbed. Praying for KWD" Spicer said.