"A few horses I was booked to ride didn't get in; they were on the reserve list," the rider explained.
The Australian ace's five mounts on the nine-race card is one less than his next lowest this term, but could have been only four. The withdrawal of Brave Power resulted in standby starter Winner's Heart (128lb) being promoted.
Winning Method lines up in the last, the Class 3 Hoi Yuen Handicap (1200m), and he is aiming to go back-to-back. Grant van Niekerk partnered the three-year-old for a return to form last time but misses out to Purton due to suspension.
"He's a boldly-going horse, he wants to get out there and get on with it to get things done, we've seen that at the races as well," he said.
The Danny Shum-trained galloper will break from gate nine against a hot field of 12 which features six other horses who have already won this season, including two with multiple successes.
"It's a bit of an awkward barrier but his last win was solid and if he can repeat that performance he's got a chance again," Hong Kong's three-time champion jockey said.
The Holy Roman Emperor galloper showed promise as a griffin late last term but was gelded in the off-season and disappointed when defeated in his first two starts; eighth as a dominant 1.6 favourite and then seventh as a 3.3 favourite.
"After being gelded, some horses need time to recover and this is why he didn't return at his best," Shum said.
The addition of blinkers have also aided the three-time winner, striking at his third attempt with them last start when holding off a competitive field that included Snap Fit, Shining Ace and Baby – all winners at the Valley this season.
"The blinkers have helped him as well as being gelded, so it took him a few runs to feel better but now he's shown that he has returned to form," Shum said.
With a fair bit of pace in the race, coming from the likes of Speed Vision (133lb), Quadruple Double (128lb) and Relentless Me (117lb) - Shum indicated that his tactics could be altered to accommodate his charge.
"His form is consistent, the only issue now is that he has drawn barrier nine but hopefully he can jump, go forward and maybe follow Quadruple Double but he has a chance again," he said.
Purton, meanwhile, has 54 wins on the board and is having a stellar term by anyone's standards but Hong Kong's reigning champion jockey is a little unsatisfied with his first half of the season.
"It's going ok after a frustrating start to the season - a couple of suspensions halted my momentum and the big horses haven't quite turned up, as well as the stables I ride for being a bit quiet," he said.
Purton is five behind Joao Moreira who leads with the premiership with 59 wins as the half-way point comes into view.
"It is what it is but hopefully that means it's all going to come together in the second half of the season," he added.
Beyond Wednesday's card, Hong Kong racing will continue on Monday (27 January) with the HK$10 million Hong Kong Classic Mile (1600m), the first leg of the Four-Year-Old Classic Series.
That race has eluded the decorated jockey, who will ride the Tony Cruz-trained Star Performance this time. The gelding won at the tail-end of last season but has gone winless across five appearances this campaign.
"He's been disappointing, last time he had the pace to suit, he relaxed nicely with the right run and he came into it as if he was going to produce something special but he just didn't finish it off," Purton said.
"Tony's going to tinker with the gear, he's got the engine, he's got ability it's just a matter of whether he's going to do it but he should be competitive."
The Per Incanto gelding will face an expected field of nine entered for Monday's feature, including Golden Sixty, Champion's Way, Beauty Legacy and More Than This.
Wednesday's nine-race card at Happy Valley commences at 6.45pm with the Class 5 Yue Man Handicap (2200m).