"Unless a miracle happens, it looks like it's going to be too tough," the champion jockey said this morning, Friday, 12 July.
But if Moreira is the "Magic Man", Purton has this season shown a knack for pulling off the miraculous, not least when producing a stunning six-timer at the big track last weekend - his fourth six-win haul this term.
Whether or not he breaks the record, he has enjoyed a superb season. Aside from his 166 wins so far - an incredible tally for a rider who rarely rides below 120lb - he has partnered Hong Kong's superstar Beauty Generation through an eight-win unbeaten sequence and struck up a top class partnership with leading stayer Exultant.
"It's hard not to be happy with it," he said. "It's ended up being better than I thought it could ever be. I never thought I could get to the mark that I'm at so that's an achievement in itself and one that I'm very proud of. All round I've had a good season. It's going to be hard to replicate it but hopefully I can."
Purton benefitted from the absence of fellow three-time champion Joao Moreira through the first three months of the season but he has also made the most of his opportunities - and he has ridden brilliantly.
"The expectation was there at the start of the season," he said. "It always looked as though it was going to pan out the way that it has to a certain degree, so to get out there and get the job done is very satisfying. But, at the end of the day, it just comes down to the opportunities I get. It's the same for any jockey, if you can't get on the right horse you can't win races. I've had plenty of support this season, I've been able to capitalise on that and things have gone well."
Purton has 10 rides booked on Sunday, including four for John Moore, who is throwing all he has at overhauling John Size in the race to be champion trainer. Among that quartet, the Australian hoop will be aboard Good Standing (126lb) in the afternoon's feature, the Class 1 Sha Tin Mile Trophy Handicap (1600m).
"Good Standing feels pretty good, it just comes down to the circumstances of the race," he said of the five-year-old, who he rode to victory in the Class 1 Hong Kong Macau Trophy Handicap (1400m) two months ago.
"That race did work out well for him," Purton continued. "I don't think he needs to have a solidly-run race for him to be effective. I think it's a matter of him sitting in the right spot; it's more a case of having him feel comfortable and he'll give his best that way."
The hot field of 11 also features the talented Ka Ying Star (127lb) from the Tony Cruz stable, and Dinozzo (129lb), Time To Celebrate (123lb) and Raging Blitzkrieg (113lb) from the Size yard.
The season finale action starts at 12.30pm with the Class 5 Medic Kingdom Handicap (1800m), in which Purton is booked for the Moore-trained Above, and concludes at 5.50pm when the champion jockey will partner Moore's Thanks Forever in the Class 2 Hong Kong Racehorse Owners Association Trophy Handicap (1400m).