Brisbane trainer Robert Heathcote admits there is a doubt over dual Toorak Handicap winner Solzhenitsyn running out the 2000 metres in the Mackinnon Stakes at Flemington on Saturday.

But, in the next breath, Heathcote says that although Solzhenitsyn has never raced over the distance since joining his stable, he and jockey Nash Rawiller think the big seven-year-old is up to the task.

"Both Nash and myself are confident he will see it out," said Heathcote.

"It's one of the strongest fields in years - chockful of quality horses."

Heathcote is enjoying a great spring with Queensland Horse of the Year Buffering finally breaking his duck in Group One races with victory in the Manikato Stakes.

Solzhenitsyn saluted again in the Group One Toorak while his grey mare Fire Up Fifi won the Group Two Blazer Stakes.

Heathcote has no regrets about not paying up to run Solzhenitsyn in last Saturday's $3 million Cox Plate.

"We had made the initial payments but the owners decided they would be more comfortable running in the Mackinnon," Heathcote said.

"He's already achieved his goal, won (the Toorak) back-to-back, and now we're happy to go on to the Mackinnon."

Last year the son of St Petersburg took the Group One Emirates Stakes (1600m) option where he finished sixth behind Happy Trails, a Mackinnon Stakes rival.

"We feel the distance better suits the horse," Heathcote said.

"We know he is a successful miler, but, being a handicap, the Emirates certainly makes it harder."

Heathcote said Buffering pulled up in great order after the Manikato and will run in the Group One VRC Sprint Classic on Saturday week before heading to Perth for the Winterbottom Stakes.