Michael Walker's hopes of winning the Victorian jockeys' premiership are all but over with the leading rider sidelined due to a recurring back injury.

Walker, who trails Dean Yendall by four winners in the premiership race, will out of the saddle until at least next week.

He was stood down with the injury at Mornington on June 8 and only took the one ride at Moonee Valley last Saturday.

Walker said he was able to get through the race without a problem but afterwards he was in severe pain.

Walker is having constant physiotherapy and chiropractic treatment on a prolapsed disc and he is taking antibiotics to help clear a kidney complaint.

"The muscle spasms are really what are keeping me out of riding," Walker said.

"The disc hits the nerve and then it spasms.

"My chiropractor says it could be two days, two weeks, it might be two months, it might be two years. It's one of those things you just don't know."

Before he was forced out of the saddle, Walker led Yendall 127 to 125 in the premiership race.

Walker also sits in fourth place on the Australian table with 128 winners, trailing the pacesetter James McDonald who is on 140-1/2.