Jockey Luke Currie will have to rely on topweights Snow Sky and Protectionist missing the Caulfield Cup if he is to ride Magnapal in the $3 million race.

The Terry and Karina O'Sullivan-trained gelding won his way into the Caulfield Cup with his victory in Saturday's Naturalism Stakes.

But chief handicapper Greg Carpenter has left him on 50kg, outside Currie's weight range.

Snow Sky and Protectionist head the Caulfield Cup weights on 58kg but if the two don't run, weights will need to be raised one kilogram.

Currie said on Sunday he could get down to 51kg.

"It was a competitive renewal of the Naturalism Stakes again this year but with Magnapal winning on the limit weight it was difficult to get him any higher in the handicap for the Caulfield Cup, Carpenter said.

Magnapal's other chance to earn a weight increase will come in the JRA Cup at Moonee Valley next month with the winner liable for a penalty.