A few questions lingered after Buffering broke through for his first Group One win two weeks ago.

But none remained after his second at Flemington on Saturday.

Buffering answered every query in the VRC Sprint Classic (1200m), jumping to the front and leading every step of the way, his three-quarter length margin a fair measure of his standing among Australia's sprinters.

While the three-year-old Zoustar has the potential to be the country's best sprinter, there is no doubt in trainer Robert Heathcote's mind that Buffering is the No.1 this spring.

"There's no Black Caviar, no Hay List. But there's a Buffering," said Heathcote.

Buffering had run 10 Group One placings before winning for the first time at the top level in the Manikato Stakes at Moonee Valley two weeks ago.

But Heathcote agreed that win had been less than dominant.

"There were probably a few unanswered questions after the Manikato ... a thought that he might have been a little bit lucky," Heathcote said.

"But there was no luck in that today. That was pure guts, determination and ability."

Buffering ($11) was clearly supreme under weight-for-age conditions down the Flemington straight course, holding off the late run of Newmarket Handicap winner Shamexpress ($18).

Moment Of Change ($9) held his position throughout to finish third, 1-3/4 lengths further back.

The favourite Lucky Nine, a close second to Buffering in the Manikato, proved the major disappointment, finishing sixth after having every chance.

His trainer Caspar Fownes said he would return to Hong Kong for next month's International Sprint.

Buffering, which has now won a leg of the Global Sprint Challenge, won't seek the bonuses attached to success in further legs of the series.

Heathcote said next year's International Sprint in Hong Kong could be on the cards, but he's unlikely to target Royal Ascot next June.

As impressive as Buffering has been, his rider Damian Browne hasn't been far behind in Melbourne this spring.

Browne has won six races from 19 rides during the Melbourne carnival, with notable victories also coming on Liesele and Missy Longstocking.

Browne said Buffering had run his usual, honest race.

"At the crossing I got them off the bit pretty good," he said.

"And when I asked him for a kick he gave me a quick length.

"He gives everything, every time. That's what sets him apart - his honesty."