James McDonald has received a dressing down from stewards at Canterbury over his handling of the Chris Waller-trained Radiator in Wednedsay's final race.

The mare was badly held up for a run in the straight before McDonald eventually changed course to the inside and Radiator made late ground for fifth to Lisa Lost It.

Stewards were critical of McDonald, who they felt persisted for too long in waiting for a gap to open between rival runners.

McDonald admitted his ride was poor but added he was unable to change course sooner because he was on heels.

"As soon as I got off I said it was a bad ride. I just stuffed up," McDonald said.

Stewards agreed and said they had no concerns over the integrity of McDonald's effort but added they expected better judgment from a rider of his calibre.

"You've made an error of judgment," presiding steward Marc van Gestel told McDonald.

"In future we expect far greater judgment and more decisiveness in your rides."