Champion trainer John Size may hold all of the aces for Sunday’s Group Two Jockey Club Sprint, but it is his former prodigy Frankie Lor Fu-chuen who has the joker in the pack.

It is Lor’s speed machine Mr Stunning, perhaps Hong Kong’s most proven Group-level sprinter, who is the greatest danger to the five-strong army of Size gallopers after a sizzling barrier trial last week.

Ironically, Mr Stunning only made his way to Lor’s yard from Size’s stable late last season with the 10-time champion trainer stuck with an embarrassment of sprinting riches.

Despite continually knocking on the door, Lor is yet to break through for a Group level victory in his short training career but takes a strong hand to Sunday’s meeting in preparation for the Longines Hong Kong International Races.

Mr Stunning impressed first-up last month in the Group Two Premier Bowl (1,200m), running an eye-catching third behind Hot King Prawn while giving up an 11-pound weight disadvantage.

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“Last time he was first-up so he wasn’t really 100 per cent fit, only around 80,” Lor said.

“After his last run I gave him one more trial and he trialled well. This Sunday I think he should be much better.

“It’s my second season so I really hope to win some Group races.”

Jockey Karis Teetan is also hoping his gamble can pay off after he jumped off Hot King Prawn earlier this season to honour a commitment made to the owners of Mr Stunning.

Rarely running a bad race, Mr Stunning has only missed a placing twice in his 11 career starts at Group level, while also winning last season’s Group One Hong Kong Sprint along the way.

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“He’s one of the best sprinters in Hong Kong and I still believe he can win a race like this,” Teetan said.

“On his last run I would say he has still got some energy inside. He came from John [Size] and John did not kill him and he’s only had one run with Frankie, so the horse still feels good and he feels very healthy.”

Teetan believes last week’s barrier trial could be the difference for the six-year-old after he forced the issue, running a lighting quick 44.4 second final 800m.

“Frankie needed the horse to have a good blow as he tends to go so easily all the time,” he said.

“He felt great in the Premier Bowl but he definitely needed the race and a good trial like last week was just what he needed.”

Lor will also saddle up Glorious Forever (Joao Moreira) in the Group Two BOCHK Jockey Club Cup (2,000m), hoping to turn the tables on his older brother Time Warp after the pair finished one-two in the Group Three Sa Sa Ladies’ Purse.

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“I need to think about my approach,” Lor said.

“Last season when he raced at 2,000m, he just followed the leader. But Time Warp is not easy because if you allow him to dictate, when you come at him, he will go again.

“But he looks like he has improved after his last race.”