Leading Sydney jockey Brenton Avdulla has suffered a lower back injury in a barrier trial incident at Randwick.
Avdulla was dislodged on the way to the stalls and then trodden on when he was on the ground.
He will have tests to determine the extent of the problem and whether he will be fit to ride at Warwick Farm on Wednesday.
After four winners on Saturday, Avdulla holds a 13-win lead over Blake Shinn in the Sydney premiership after missing out on the title last season when Hugh Bowman overtook him in the final couple of weeks.
Fellow jockey Kerrin McEvoy is receiving treatment on his right hand which was pinned against the barrier stall before a race at Doomben on Saturday.
McEvoy originally feared a repeat of the broken hand which kept him out for six weeks earlier this season but told RSN 927 he believed it was ligament damage only.
Like Avdulla, McEvoy has been booked for rides at Warwick Farm.