Trainer David Hayes has tipped Criterion as a potential Cox Plate winner this Spring after the four-year-old finished a brave fifth in the Prince of Wales's Stakes at Royal Ascot.

Favourite Free Eagle took the Group One win despite having been off the track since October, holding off a fast-finishing The Grey Gatsby by the barest of margins.

Hayes said if Criterion had relaxed more in the middle stages he could have ran third.

"He looked like he was going to get beaten by a good margin and he kept kicking back and just missed fourth," the Australian trainer told reporters.

"I thought it was a pass mark without raving. He was competitive but wasn't quite good enough."

Criterion was a bit fresh before the start but will be better for the run.

The connections will now consider giving him another race in England.

"We were thinking the Sussex Stakes which is a bit of a faster tempo mile," Hayes said.

"I reckon he might be a good miler here but we'll just let the dust settle and see what we do after."

Criterion will later head home for the Spring racing carnival.

"He'll come home for the Spring I think," Hayes confirmed on Wednesday.

"He's a horse that I think is an ideal Cox Plate horse. He could run very well in it.

"Horses that ran sixth or seventh in this would be favourites in it - like he would be."

Criterion, one of the early favourites for the 2000m Prince of Wales's, had drifted to 20-1 by the time the nine horses jumped.

Australian-based Chad Schofield, who won the Cox Plate in 2013, was in the saddle.

The Hong Kong-bound jockey rode Criterion in track work ahead of the race and was a surprise pick ahead of Damien Oliver and Craig Williams.

Schofield said Criterion had a beautiful run with good cover throughout.

"He came off the boil nicely like he was going to sprint and be right in the finish then he just sort of peaked on his run a bit," the 21-year-old told reporters.

"But he was brave to keep battling."

The jockey thinks Criterion, who could potentially go to stud before next year's Ascot meet, still has a lot of improvement in him.

Hayes in his first visit to Ascot in 2010 secured a fourth place with Nicconi in the King's Stand Stakes.

After Criterion finished fifth on Wednesday the 52-year-old said he'd always consider returning "with the right horse".

"I've been competitive twice but no bananas."

Sprinters Brazen Beau and Wandjina will fly the Australian flag in the Diamond Jubilee Stakes on Saturday.