Former champion jumps jockey Mathew Gillies will be a notable absentee from this winter's action.

The 31-year-old, who won the premiership in 2013-14, will be side-lined after undergoing knee surgery.

"I'll be out for the season, but I will be looking to come back for the next one," Gillies said.

The Cambridge-based rider had only just made a full recovery from the effects of a nasty fall from Gagarin in last July's Wellington Hurdles when he suffered his latest setback.

Gillies was concussed and copped a bad head gash when he came to grief in the Trentham feature.

"I wasn't right after taking that knock and it took me six months to feel 100 per cent again," he said.

"I came back to ride work and then twisted my knee and I had to have an operation on my ACL (anterior cruciate ligament)."

Gillies said he had given thought to retirement after his latest injury problem, but he is now committed to a return to the saddle.

"Hopefully, I can come back in late August or September and ride a few quiet ones in work to start off again."

The son of former successful jockey and current trainer Stephen, Gillies has a career tally of 85 winners and in recent seasons he has enjoyed a successful association with the powerful Kevin Myers stable.