Having failed to make the cut for the Queensland Derby, Ombudsman has shown he is a stayer of promise by beating older horses to win the Winter Racing Handicap at Randwick.

The Chris Waller-trained three-year-old travelled midfield before emerging from the pack to score a decisive win in Saturday's 2400m-race.

Sent out at $4.40, Ombudsman had 1-3/4 lengths to spare on Only Tiger ($7) with race leader Diamond Star Halo ($19) holding third, another 1-1/2 lengths away.

"He was an emergency for last month's Queensland Derby and didn't get in but today he has shown he can stay the distance," Waller said.

"I think he can be a minor Cups horse in the spring in New South Wales.

"I think he would be an ideal horse for a race like the Newcastle Cup."

Waller said Ombudsman might have another run before the end of the month which is also the end of season.

"He may have one more but we are mindful he is a three-year-old against the older horses," he said.

"We will just see how he is."

Plymouth Road ($4.60), the winner of a similar race two weeks ago, tailed off and finished almost 32 lengths from the winner.

His jockey Adam Hyeronimus said he had been hampered three times during the race and had nothing left to give in the straight.

Ombudsman is by 2011 French Derby winner Reliable Man who Waller subsequently trained to win the 2013 Group One Queen Elizabeth Stakes at the second and last of his two Australian starts.