Sebastian Murphy, who hasn't ridden in a race for over four months, is working towards a comeback.But just when that will be hasn't been decided.Murphy, who turns 19 on January 1, suddenly stopped riding at the end of August suffering from mental and physical exhaustion. His mother and manager Marita Murphy said he needed an indefinite rest.He has been back riding trackwork and in jump-outs at Ballarat and stepped it up with eight rides at Tatura barrier trials last week.Murphy also rode in tria

Sebastian Murphy, who hasn't ridden in a race for over four months, is working towards a comeback.

But just when that will be hasn't been decided.

Murphy, who turns 19 on January 1, suddenly stopped riding at the end of August suffering from mental and physical exhaustion. His mother and manager Marita Murphy said he needed an indefinite rest.

He has been back riding trackwork and in jump-outs at Ballarat and stepped it up with eight rides at Tatura barrier trials last week.

Murphy also rode in trials at Colac on Monday.

"He basically hasn't got a clearance to ride in races yet," Marita Murphy said.

"He had back issues and during his break he had a CAT scan and it revealed he had a bulging disc and until his back is right he can't run and he can't address his weight."

Murphy has managed to keep his weight in check at around 60kg with swimming and lots of walking as well as physiotherapy for his back complaint.

Racing Victoria Ltd consultant medico Gary Zimmerman has put Murphy on light duties and the apprentice is still taking anti-inflammatories.

The problem was aggravated by two incidents at the races, the first when two-year-old filly Ortensia reared over in the mounting yard before the Blue Sapphire Classic at Caulfield on May 10, a race she was withdrawn at the barrier from.

"They threw him on her after that and she was cranky and galloped flat out to the barrier and he didn't have his feet in the irons, so that was probably a starting point," his mother said.

"He hasn't had any falls here with his boss (Darren Weir) but a horse he rode for him at Geelong in August called Grease Monkey whipped around at full gallop after a race and flung him off.

"He hung onto the reins but got whiplash. He had nine races that day and seven or eight the next day at Caulfield.

"When you're hot you want to keep going but that was the beginning of the end.

"He had had back issues but thought he was managing them with physio but it all got too much for him."

Murphy, who had been riding at 53kg, was suspended for careless riding aboard the Lee Freedman-trained Dane Julia in the Cockram Stakes at Caulfield on August 16 and hasn't ridden since.

The son of jockey Garry Murphy, he has been Victoria's leading metropolitan apprentice for the past two seasons as well as finishing runner-up to Craig Williams in the jockeys' premiership.

He has ridden 307 winners, including 114 in the metropolitan area.

Murphy rode his first Group One winner aboard the Mike Moroney-trained Mr Baritone in the Stradbroke Handicap at Eagle Farm earlier this year.

Murphy rode four winners at Sandown on May 6, 2007 and landed his first Group winner on his 18th birthday when Publishing won the Standish Handicap at Flemington.