The Ballarat teenager Murphy has been sidelined indefinitely with exhaustion and sitting out the entire spring has not been ruled out.

Murphy's mother Marita told The Courier yesterday that it was impossible to predict when the 18-year-old might return to race riding.

"We just don't know."

She said while it was disappointing to be out at the biggest time of the racing season, there was no choice.

"The priority is to get him back to full health."

Ms Murphy said it appeared the hectic pace being set by the two-time Melbourne metropolitan premier apprentice jockey had caught up with him.

She said he had been doing a great job, but indicated her son would have to re-evaluate his workload when he returned to the saddle.

The champion young jockey has twice had glandular fever, but at the time of speaking to The Courier his mother was uncertain whether there was a link to his existing condition.

Murphy is apprenticed to Darren Weir at Dowling Forest and was last season crowned Victoria's champion apprentice.

Murphy also rode his first group one winner last season - the Michael Moroney-trained Mr Baritone in the $1 million Stradbroke Handicap at Eagle Farm in Brisbane.

He also rode in the Melbourne and Caulfield Cups last spring.

Murphy announced at the end of last season that as well as maintaining his commitment to the Weir stable, he was planning to ride trackwork for Moroney at Flemington once a week in the hope of getting more rides in bigger

races.

Murphy has not ridden since August 17 after being suspended for 14 race meetings at Caulfield on August 16.

He was scheduled to return to riding until next Monday.