The approach David Hayes is taking into Saturday's Vase at Moonee Valley is probably the same as most trainers with a runner in the race.

Hayes, who'll saddle up Prisoner Of War in the Mitchelton Wines Vase (2040m), knows Group One-winning colt It's A Dundeel will be extremely hard to beat.

But he hopes to catch the New Zealand stayer on a bad day with Prisoner Of War, one of four horses entered coming out of the Hill Smith Stakes in Adelaide at their last start.

"I think if the favourite has an off day, then he can be very competitive," Hayes said of Prisoner Of War.

It's A Dundeel so far hasn't had an off day though. And even if he has, he's still won.

But defeat may not necessarily spell the end of Prisoner Of War's Victoria Derby ambitions.

Hayes trained Kibbutz to win the 2007 Victoria Derby, using the Hill Smith Stakes in Adelaide and a Vase placing as a springboard to success in the Classic.

It's A Dundeel takes in an unbeaten record of five wins from five starts including the Group One Spring Champion Stakes at Randwick earlier in the month when he defeated Proisir.

Proisir is among the fancied runners in Saturday's $3 million Cox Plate.

The Vase gives the $1.25 favourite It's A Dundeel the chance to race in Melbourne ahead of his major goal, the Group One Victoria Derby.

It's A Dundeel's jockey James McDonald fired an ominous warning earlier this week saying the colt, if anything, had come on since his Spring Champion Stakes win.

Efficient (2006), Plastered (2004), Helenus (2002), Blevic (1994) and Raveneaux (1986) have completed the Vase-Derby double.

The ill-fated Lion Tamer, who was prepared by It's A Dundeel's trainer Murray Baker and his son Bjorn, was runner-up in the Vase two years ago on his way to winning the Derby.