One of the fastest first 500 metres of a race at Canterbury in 14 years helped bring about the failure of odds-on favourite Betrayal on Wednesday.

The three-year-old ran last in his 1100m race in which he ran 28.10s for the first 500 metres.

"That's the third or fourth fastest time at Canterbury for 14 years for the first part of a race," betting steward Terry Griffin said.

Betrayal was having his first start for trainer Bjorn Baker and went into the race off the back of an eight-length win in a barrier trial.

He was subsequently found to have respiratory distress and a poor post-race recovery.

Baker said he would give the horse a thorough veterinary examination and stewards said they would hold off on any decision on whether Betrayal should be made to trial until after that was done.

"He only knows one speed and that's full speed," Baker said.

Betrayal's jockey Brenton Avdulla escaped with a reprimand after pleading not guilty to a careless riding charge in the first part of the race.

Stewards found he had tightened No Bad Blood on the first turn in the race won by Chiaramonte.