Zac Purton has expressed his frustration over Massive Sovereign’s 25-point ratings hike for winning the BMW Hong Kong Derby (2,000m), a figure handicapper Ian Malpass has confirmed Jockey Club officials are “comfortable with based on historic ratings”.

The Dennis Yip Chor-hong-trained gelding’s rating soared from 82 to 107 in the wake of his outstanding victory in Hong Kong’s most prestigious race on Sunday.

Purton, who won his second Hong Kong Derby when Massive Sovereign beat Galaxy Patch and Ka Ying Generation in a thrilling finish, was miffed by the penalty.

“I just don’t understand it, I really don’t,” Purton said. “It would be nice if the handicappers came out and explained. He’s now 24 points ahead of Ka Ying Generation for a half length difference.

“I don’t know how you work that out. In reality, it’s not going to matter because he’s going to run in set-weights races, but it’s not the point. The point is they need to explain how they came to that.”

Purton is aware of the Jockey Club’s policy of handing beaten gallopers a maximum penalty of five points.

After almost pinching the Derby courtesy of a bold front-running ride by Andrea Atzeni, Ka Ying Generation was penalised the maximum five points.

Malpass, the Jockey Club deputy executive manager of handicapping and race planning, said Massive Sovereign’s low rating before the Derby and recent history of Derby winners led to the 25-point penalty.

He also pointed to Galaxy Patch’s slashing second to California Spangle in the Group One Queen’s Silver Jubilee Cup (1,400m), which gave him a rating of 103 before the Derby.

“One of the challenges for handicappers worldwide is to come up with reasonable, and just as importantly justifiable, post-race ratings following the running of races run under set-weights or non-handicap conditions,” Malpass said.

“With this year’s edition we saw an extremely progressive winner who has no ceiling at this stage, being two from two in Hong Kong and looking like he can be competitive at the top level.

“The runner-up, who was second in an open-age Group One at his previous start, has already proven he is capable of performing at that level.

“Ultimately, we settled on 106 for Galaxy Patch, which is still well below where we had him performing in the Queen’s Silver Jubilee Cup last time. The winner, who was a neck in front, was taken a pound higher to 107, a figure we were also comfortable with based on historic ratings and the quality of his performance in this race.

“The third [placegetter], who ran a very bold race from the front, was taken to 83, which under the current policy is the most allowed, with beaten horses only permitted to be improved five pounds.”

Massive Sovereign was only the third galloper rated under 100 to win the Derby in the past 24 years. Voyage Bubble won off a mark of 93 last year and copped a 10-point hike, while Keen Winner was dealt 24 points for his victory in 2000 off a mark of 92.

Purton delivers on Massive Sovereign in Hong Kong Derby for the ages

“When you look back at the subsequent performance of recent Derby winners, their post-race figure is usually below – and in some cases well below – where their peak figure ultimately ends up,” Malpass said.

“Seven of the past 10 Derby winners ended up with peak domestic figures of 123 or higher, all of which improved significantly after their Derby wins. The biggest improvers being Romantic Warrior (102 to 132), Voyage Bubble (103 to 125) and Golden Sixty (112 to 131).

“Given the way both Massive Sovereign and Galaxy Patch have performed so far, we would be extremely hopeful both horses can also reach that sort of level by the end of the season.”