The benefit of extra muscle and the absence of a notable opponent has given trainer Danny O'Brien the confidence to tip a return to top form for his talented sprinter Shamexpress at Flemington on Saturday.

Shamexpress has been unplaced in three of his four starts since winning last year's Newmarket Handicap, a victory that earned him a trip to England.

The four-year-old returns to racing in the Group One Lightning Stakes (1000m) after a brief spring preparation that indicated his travels had done him no harm.

"He's bigger and stronger than he was last year and he's not taking on Black Caviar," O'Brien said.

"I'm glad he's turning up here on Saturday."

Shamexpress finished sixth to the champion mare in last year's Lightning before winning the Newmarket three weeks later.

He then produced a couple of indifferent efforts in the King's Stand Stakes at Royal Ascot and the July Cup at Newmarket.

But he turned in a superb effort when second to Buffering in the VRC Sprint Classic at his latest start and according to O'Brien he's held the form this time in.

"He galloped really well last Friday, he's had a great build up to this," he said.

"I'm also fairly certain he's at his best down the straight here at Flemington, so there's a lot to look forward to."

Shamexpress heads to the Newmarket second up and O'Brien will assess his options after that race with a view to another international campaign.

O'Brien confirmed his Cox Plate winner Shamus Award would go straight to the Australian Guineas on March 1 after his promising return to racing when third in the Orr Stakes at Caulfield last week.

"He's in as good a shape as he's ever been," O'Brien said.

"He might have been out of his comfort zone a bit earlier than we'd hoped in the Orr, but he'll be at right for the Guineas."