Champion jockey AP McCoy is set for at least a further two weeks on the sidelines, which could end his pursuit of a historic 300 winners in a season.
McCoy, who has ridden 152 winners so far, has been troubled by the effects of a fall at Worcester in October.
He aggravated the injury in another fall at Exeter on Tuesday and is resigned to a spell out of the saddle.
McCoy, 40, told BBC Sport: "I would imagine it would probably be two weeks before I go back to see the doctor."
McCoy, who reached the milestone of 4,000 winners at Towcester a year ago, was targeting 300 successes this season.
The 19-time champion jump jockey was slightly ahead of schedule when he recorded his 150th on Goodwood Mirage at Wetherby on 15 October but has just had two winners since then.
|Champion jockey AP McCoy:|
|"The most pain I'm in is that I can't go racing tomorrow."|
"I was trying to go through the pain barrier because I didn't want to take time out because I had the hope of that dream of trying to ride 300 winners," added McCoy.
"I have had my best ever start to a season and when you get that close to something it's very hard to try and give it up.
"But I knew after I had a fall on Tuesday and after seeing the doctor on Thursday that I would have to have some time out and get myself back right again.
"There is a long season ahead and my boss JP McManus has a lot of good horses he will want me to ride and it's important I get back to riding them.
"Sadly I will have to sit it out for a couple of weeks, which is not good mentally or physically but probably mostly mentally at the moment."
McCoy now looks set to miss Cheltenham's prestigious three-day fixture featuring the Paddy Power Gold Cup that starts next Friday.