Tyler Schiller has been involved in a dramatic pre-race incident at Canterbury.

Top jockey Tyler Schiller has been taken to a Sydney hospital with a suspected back injury after being dislodged from his mount in the opening race at Canterbury.

Schiler was aboard debutante Rockabye Roxy for Gary Portelli when the filly bucked shortly after going onto the track, tossing Schiller over her neck.

He landed heavily and remained prone on the track as paramedics attended to him but remained conscious throughout and was moving his legs.

Schiller was transported to Royal Prince Alfred Hospital for further tests and was stood down from his remaining rides.

"He's got a back injury. They will obviously identify the significance of it when he gets to hospital and has the appropriate assessment," Racing NSW chief steward Steve Railton said.

Schiller is booked for seven rides at Eagle Farm on Saturday, including Gallo Nero, the early favourite for the Group 2 BRC Sires' Produce Stakes (1400m).

Portelli reported that Rockabye Roxy was unharmed in the incident, although she was a late scratching.

The other horses had made their way to the starting stalls and officials were forced to order them back to the mounting enclosure and delay the first race by 35 minutes as they waited for a second ambulance to arrive on course.

The Ranvet Handicap (1100m) was eventually won by the Terry Croft-trained Gilette ($41), who had finished runner-up in her two previous starts at Bathurst and the Inglis Challenge at Scone.

A $16,000 buy, the daughter of Exceedance took her career earnings past $70,000 with Wednesday's win and will now head to the paddock.

"She has always shown us good ability. Her second trial at Rosehill she ran second but the horses that finished behind her have run in Group races," Croft said.

"She is going to the paddock. She needs to mature and develop.

"But I can't fault her form, three starts, two seconds and a win."