Hillsin’s run, under Dylan Kitts, caught the attention of stewards, who held an inquiry into his performance.
They noted the horse, trained by Chris Honour, “travelled strongly” in the home straight “without appearing to ever be asked for a finishing effort”.
Kitts said the horse made “respiratory noises” during Wednesday’s race.
He said Hillsin had hung to the right while running, which also restricted his ability to be more vigorous in the home straight.
Hillsin, who had been 2-1 favourite on Tuesday night and drifted in the betting to start at 11-1, finished one and a quarter lengths behind winner Bensini in the conditional jockeys’ handicap hurdle.
Honour said the rider had generally followed his instructions to take his time, before mounting a late challenge although he did “express concerns over the manner in which Hillsin was ridden specifically from jumping the last hurdle”.