David Hayes is counting down the days to the Cox Plate after Criterion returned to Australian racing in brilliant fashion to win the Group One Caulfield Stakes.

Criterion won this year's $4 million Queen Elizabeth Stakes at Randwick before embarking on a three-race overseas campaign, firstly in Hong Kong and then two starts in England.

After finishing fifth in the Prince Of Wales's Stakes and sixth in the Juddmonte International, Criterion returned home with the first shipment of overseas horses to arrive for the spring carnival.

He completed quarantine on Saturday morning.

Hayes says Criterion can win the Cox Plate and the horse has firmed from $11 to equal $5 favourite alongside Kermadec which finished fourth the 2000m weight-for-age race.

"I think he can (win the Cox Plate). We've gone into the race fresh and I just said to my wife - 14 more sleeps," Hayes said.

Criterion's victory didn't surprise Hayes.

"I think he's been racing in the Olympics and he's back in the National Championships now," Hayes said.

"People just don't understand how good they are over there."

Suspension cost Michael Walker the ride on Criterion first-up in the autumn carnival in Sydney but he got his chance on Saturday and made it count.

Criterion ($7.50) settled second last in the field of eight with Entirely Platinum leading and Fawkner and Pornichet handy to the speed.

Criterion improved out wide from the 600m with Happy Trails ($16) and they battled it out in the straight with Criterion edging clear late to win by a half length.

Mongolian Khan ($13) is the new Caulfield Cup favourite after hitting the line strongly to finish another half-head away third.

"For me it was unfinished business," a delighted Walker said.

"I was supposed to ride him last preparation but it didn't happen (because of suspension). In my first ride on him to get a Group One, I'm thrilled."

Glen Boss is happy with the way Kermadec is going towards the Cox Plate but felt the track, which he described as firm, played against him.

"His best form is when he gets his toe in the ground. As far as everything else, he's going well," Boss said.