A more muscular Amber Sky made a stunning return to form with a scintillating Sha Tin straight-track win on Wednesday that thrust Ricky Yiu Poon-fai's former boom juvenile into international day reckoning.

Amber Sky entered the parade ring looking like a different horse as a four-year-old - weighing nearly 70 pounds more than he did at his last start. The son of Exceed And Excel then scorched the turf with new jockey Joao Moreira aboard - setting a breakneck speed and then clicking up a few extra gears late as he scored his fifth career win in a slick time of 55.81 seconds.

A 51/2-length winning margin should attract a double figure rise in the handicaps up off a current mark of 99 and put Amber Sky right in the mix for the Group Two Jockey Club Sprint on November 17, followed by the Group One Hong Kong Sprint in December.

"He has gone up more than 60 pounds in body weight - but he hasn't stopped working and it is all muscle," Yiu said. "I'm pretty confident he can step up and compete in those big races and in the Hong Kong Sprint - if they pick him. Let's see how much they put him up in the ratings."

Amber Sky won all three starts as a two-year-old, but struggled through his second term, winning just one of seven and scoping with substantial blood in his trachea when a disappointing 11th at his last start.

Moreira - who rode the sprinter in a lead-up trial - felt there was even more left in reserve. "It's very exciting to see how he will improve for his next race - today he was too good for them," he said.

Both Yiu and Moreira had a double - winning earlier on Namjong Blossoms - but the jockey's night was soured somewhat when he received a three-meeting ban for his ride on Dashing Super in race four. Moreira deferred his suspension until after the Jockey Club Sprint - but will now have to decide between riding Amber Sky and Sterling City in that race.

Both the championship frontrunners maintained their leads - trainer Manfred Man Ka-leung producing a double and Zac Purton kicking five clear of rival Douglas Whyte with a treble.

Purton helped Yiu notch a double with Great Spirit, after victories on Highest Acclaim for Caspar Fownes and a straight-track victory on debutante Devine Ten for Me Tsui Yu-sak - who also had a double.

Despite Devine Ten's breeding - he is by Happy Valley specialist Holy Roman Emperor - Tsui says he will keep the sprinter at Sha Tin, at least while he continues to get stirred up pre-race.

"He will be staying here at Sha Tin, he got very stirred up putting the saddle on him and I don't want to put him on the transport to go over there to Happy Valley," Tsui said. "Eventually he will get up to 1,400m, maybe more, but we will come back to 1,200m or 1,000m again next start."

Apprentice Dicky Lui Cheuk-yin also received a three-day ban for interference in the first part of race seven, when he tried to cross on Dane Patrol. He will begin the ban after Sunday's Sha Tin meeting.