Apprentice Jordan Grob has notched his first city winner after picking up the ride on Gun Case in unusual circumstances at Sandown.

The Darren Weir-trained Gun Case was to be ridden in Wednesday's Mypunter.com Handicap (1000m) by apprentice Brandon Stockdale but after the opening race Stockdale had to relinquish the rest of his rides after injuring himself in a jockeys' room accident.

Stockdale scalded himself after he spilled boiling water on his arm and was treated on course before being transported to hospital.

Stockdale, who had been suffering from a head cold, was offered the bucket of boiling water as a way to relieve congestion in his head.

Grob, who is currently on a three-month loan to Caulfield trainer Mick Price, picked up the ride on Gun Case and got the job done on the $8 chance to win by a short neck.

"It was unfortunate that Brandon Stockdale couldn't ride it but it's nice to get a win for Weiry," Grob said.

"It's my first Melbourne winner."

Grob started out at the Gold Coast before moving to Victoria and had been based with trainer Heath Conners at Geelong until starting his stint with Price.

"I only went down by a nose in an earlier race today for Mick on Summer Glen," he said.

"It could have been a double but a winner is a winner."

Gun Case was one of two winning rides Stockdale missed with Ben Allen guiding the Logan McGill-trained Gold Fields to victory.