Robbie Laing's belief Polanski was "an absolute certainty" in Saturday's Norman Robinson Stakes at Caulfield was justified as the colt ran down the favourite San Diego to win the Group Three contest.

In the process Polanski, who cost $4000 as a yearling, further enhanced his Victoria Derby prospects, firming to the third line of betting for the $1.5 million Classic.

And jockey Hugh Bowman is adamant the colt has "more in the tank" heading towards the 2500m Derby in two weeks.

The Laing-trained Polanski was sent out a $6 chance in the 2000m race on the back of a last-start Listed win at Flemington.

After settling with a perfect trail he went out after leader San Diego ($4.40) and was able to get home by a head.

The pair cleared out by four lengths over the rest of the field which was led in by Epic Saga ($11).

"I thought he was an absolute certainty," Laing said.

His reasoning had been Polanski was exposed too early and was at his top from a long way out last start at Flemington.

And he had improved "three to four lengths" since.

"A lot of people took away from his win because of his last 100 yards," Laing said.

"His fitness had improved and I thought if he gets a bit of cover today he'll hit the line hard."

Laing believes he has another genuine Derby contender in Dark Thunder who runs in Wednesday's Geelong Classic.

Bowman said he would be keen to stick with Polanski in the Derby.

"I just think you haven't seen the best of him yet and he's going to be a genuine Derby contender," Bowman said.