Danny O'Brien believes Portman is a future stakes-class performer after the gelding continued his consistent season with a win at Flemington.

Four-year-old Portman was sent out the $2.05 favourite in Saturday's Murray Cox Handicap and didn't disappoint.

Portman settled just behind the leaders and one off the fence before taking over at the business end of the 1400m race to defeat Orient Line ($7) by three-quarters of a length.

Rebellious Lord ($6) hit the line well for third, another 1-1/4 lengths away, after being held up on the fence at a crucial stage.

It was Portman's fourth win from 11 career starts and he has not been out of the placings in eight starts this season.

"Once he settled in that spot he was always going to be the one to beat," O'Brien said.

"He's always been a very talented horse.

"He had his first start here at the same meeting two years ago as a two-year-old and put in a terrific run from back in the field to run third.

"Then he got pneumonia and nearly died, and then he hurt his knee. So he's been in the wars but he's obviously come solid now off a good summer preparation last time in."

Portman broke his maiden at Bendigo last November in his first start from a lengthy break and has added another three wins this season, including Saturday's victory in his second start of this campaign.

"He's come back this time and it looks like he's going to go on to a good level," O'Brien said.

"I think he's certainly a black-type horse going forward."

Portman's win gave Craig Williams an early double from the first four races on Saturday after starting the meeting level with Beau Mertens in the Melbourne jockeys' premiership.