Zac Purton doesn’t ride for John Size often but when he does it pays to take note and dirt track specialist Diamond Friends looks a great chance in the Nam Sang Wai Handicap after going around riderless last start.

Diamond Friends had won just two of 22 heading into a 1,650m Class Four on September 18 but his consistency still had him rated a 5.7 chance in an even looking race, before he dumped jockey Opie Bosson at the start.

It would be pure folly to judge a horse’s “performance” after he had dislodged a rider – but going by market expectation and prior form it would seem Diamond Friends, who managed to make a nuisance of himself in the run by galloping up near the speed and contesting the finish, would have been right in the race eventually won by Good Fit.

Despite a famous victory aboard Size’s Luger in the 2015 Hong Kong Derby, Purton has only ridden sporadically for the eight-time champion trainer, but has chipped in at an efficient strike rate nevertheless.

Purton has 11 wins from 81 rides (14 per cent) since first riding for his countryman in 2007 – not bad given he has never seemingly had first choice on the runners from the leading yard.

Perhaps Purton wasn’t the trainer’s first pick here either and his main danger could be from down in the weights and Size’s usual go-to jockey Joao Moreira, who has stuck with John Moore’s Dragon Harmony.

Even though it has taken some ratings relief for Diamond Friends to win previously, his previous victories were off 45 an 46 over Saturday’s course and distance of 1,650m, a couple of decent showings late last season at around his current mark are enough of an indication the five-year-old can push into Class Three with a win here carrying 129 pounds.

From gate four Purton can park just off what should be a solid tempo set by chances Go Go Win (Brett Prebble) and Dashing Super (Nash Rawiller), drawn in the gates directly to his inside – with Faithful Boy (Jack Wong Ho-nam) a possible fly in the ointment if he wants to go forward.

If some speed does eventuate, Electronic Phoenix (Karis Teetan) could be one to watch, third-up, he returns to the scene of a fantastic first-up run in the same race Diamond Friends dumped Bosson.

Purton also rides a dirt specialist with a big weight but a chance in the following race, the Ping Shan Handicap.

Benno Yung Tin-pang’s Northern Falls is entered in a moderate Class Three and stepping up to a far more suitable 1,650m after making no impact first-up over 1,200m.

Size has stuck with Moreira earlier in the day on four-year-old sprinter Game Of Fun, who resumes over 1,200m in the Hung Shui Kiu Handicap.

The hell-for-leather tactics of straight racing a Sha Tin can be a baptism of fire for a first starters and that is exactly what Game Of Fun faced late last season as a three-year-old when sent around a 2.8 favourite in early July.

The son of Snitzel wasn’t too bad when fourth on that occasion – but he should have returned a little more seasoned and stronger after two preseason trials and finds as weak a race as you could wish for.

Game Of Fun has drawn two on the “B + 2” course in a 10 horse race where his rivals’ combined record on the Sha Tin turf is five wins from 73 starts and includes three-year-old first-starter Spicy Kaka, who, despite looking to have some potential, comes in off a trial on the wet Sha Tin dirt that wasn’t exactly confidence building.