Zac Purton has struck a speed bump in his quest to break Joao Moreira’s 170-win season record with the champion jockey forced to do it the hard way at Happy Valley on Wednesday night.

While the Australian may be able “to win on a merry-go-round” at the moment, according to race caller Brett Davis, he has drawn horror barriers in six of the nine races, with many of his best chances on the night drawing nine or worse.

From his full book of nine rides on the night, just Jumbo Happiness, Tashidelek and Perfect Glory have gates in the inside half of the field – making his task of winning seven races before the end of the season that much harder.

Zac Purton after riding Winning Delight to victory at Sha Tin for trainer Caspar Fownes.

The meeting will be the last of the season at Happy Valley, a track that Purton has ridden particularly well and has become famous for his winning mid-race moves when he senses the pace slackening off.

Purton combines for two rides with trainer John Moore, who is attempting a last-ditch run at the trainers’ championship where he currently trails John Size by one winner.

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Moore and Purton have been the most lethal combination this season, producing 33 winners from just 83 starts, striking at 40 per cent.

“It’s unbelievable, isn’t it? It seems everything we have together runs well,” Purton said.

“You see it sometimes with trainers and jockeys who don’t have many rides together but we have had plenty.

Zac Purton gallops Tashidelek at Sha Tin on Monday morning.

“I have a couple for him on Wednesday night and some for him on Sunday, they’re OK rides.”

Such has been their domination together, Purton and Moore have had more winners than they have had runners miss a placing (31) this season.

Their first runner of the night will be Touch Of Luck in the Class Four Maverick Star Handicap (1,650m) who goes to Happy Valley for the first time in his short career.

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The four-year-old has flourished since being transferred to Moore’s yard from Chris So Wai-yin earlier this season and is yet to miss a placing in four starts for his new handler.

However, it is another stable transfer in Tashidelek in the Class Three Sweet Orange Handicap (1,800m) that looks to be their best chance.

The former Jimmy Ting Koon-ho galloper was beaten as an odds-on favourite in his first start for Moore at Happy Valley and returns on Wednesday night where he drops in trip.

The four-year-old is one of the few good barriers that Purton has drawn for the night, where he will jump from gate four.

Moore will square off with Size in the race, with his four-year-old True Grit looking to make it five consecutive wins at the city track.

True Grit has been one of the stand-out performers of the second half of the season, taking his rating from 51 to 78 in the space of four starts.

Zac Purton kicks clear on Marvelous World at Sha Tin on Sunday.

The string of wins has also provided Size the ammunition needed to stay ahead in the trainers’ championship.

Size also brings his classy gallopers Tornado Twist and Special Stars back for the meeting.

Tornado Twist has been a consistent performer for Size and will return off a six-week break in the Class Two Sun Jewellery Handicap (1,200m) while Special Stars has not raced for three months.