Brett Prebble is building up a tidy bank of big race rides but the champion Australian jockey will be hoping lesser light Merion can deliver some much needed early-season momentum and a belated birthday gift in the Ventris Handicap.

Prebble celebrated his 39th birthday on Friday by climbing aboard a John Size-trained pair of feature race contenders in Contentment and Amazing Kids for all-weather track trials ahead of upcoming first-up assignments.

Contentment won the Group One Queen’s Silver Jubilee Cup for Prebble in February and the six-year-old comes back to his pet distance of 1,400m for the first time since then in Saturday’s Group Three Celebration Cup.

“Just a typical John Size-type trial, no negative, it’s just about fitness for him, he is a good horse,” Prebble said. “Amazing Kids jumped fast and showed good gate speed, that’s as good as he goes in a trial, he had a good blow and he will come on for that.”

A tough decision maybe coming for Prebble when it comes to Amazing Kids – the promising type was unlucky when running home for fifth in Chautauqua’s Group One Chairman’s Sprint Prize and was then second to Peniaphobia in the Sha Tin Vase.

Prebble is also the regular rider of Lucky Bubbles – who was put away after a second to Chautauqua and returns with expectations the five-year-old will be a Hong Kong Sprint contender.

Of Prebble’s rides on Sunday, Merion looks hardest to beat – even if the tricky Derek Cruz-trained five-year-old has found a difficult 1,400m Class Two.

“He is the best horse in the race, if he puts his mind to it and does it, he wins,” Prebble said, referring to the quirks that have stopped Merion breaking through in seven starts despite going close and starting single figures in all but one start. “He isn’t the easiest horse to ride, has blinkers on and he can pull – he needs a strong tempo.”

Prebble said barrier six is a plus as Merion returns to the same course and distance where he was second to Flying Moochi at the first meeting of the season.

“If we get that nice even tempo and can find a trail – then he will get his chance,” he said.

Neil Callan has given up the ride on Merion in favour of Consort – a horse whose expensive price tag and high profile owner, Pan Sutong, have ensured headlines throughout a mostly underwhelming six-start local career.

“Whether the whole of last season has been a learning curve and just acclimatisation, we won’t know until he gets to the races, and probably after a run or two,” Callan said of the grey, who has raced once after being gelded in late April. “At 1,400m I would expecting him to need a run.”

Consort was third over 1,600m in the 2015 Group One St. James’s Palace Stakes as a three-year-old and then fourth in the Group One Hong Kong Derby earlier this year – leading Callan to believe the son of Lope De Vega’s best trip lies somewhere in between.

Even if Callan is right and Consort is not yet at his best first-up and at 1,400m, taking the ride still comes as part of an attractive package of first call on Pan’s horses throughout the season.

That means Callan will also ride Group One winner Giant Treasure and also the option of riding a pair of European imports yet to be renamed, Royal Ascot winner Primitivo and Smuggler’s Moon.