Tony McCoy is aiming for a speedy return from injury to boost his bid to ride an unprecedented 300 winners in a season.
McCoy is still hampered by an injury sustained at Worcester a month ago and could now be out for two weeks.
The 40-year-old rode at Chepstow on Wednesday but missed out on his sole booking yesterday at Towcester - ironically the track where he rode his 4,000th winner exactly a year ago.
The Ulsterman - closing in on an incredible 20th successive champion jockey title - has already ridden 152 winners this season with six months of the campaign remaining.
McCoy was slightly ahead of schedule when bringing up the 150 on Goodwood Mirage at Wetherby on October 15.
He holds the current record of 289 winners in a season, set back in 2002.
Following news of McCoy's injury lay-off, William Hill offer 7-1 he can break his own record and 8-1 he reaches the magical 300 winners.
McCoy, who is set to miss Cheltenham's prestigious Open meeting which starts next Friday and features the Paddy Power Gold Cup, was initially sidelined for a short spell after taking a crashing fall from Keep Presenting on October 9, before returning only to be stood down after riding at Wetherby the following week.
McCoy had been in action every day since the start of the month, but he aggravated an old rib injury in a fall from If In Doubt at Exeter on Tuesday.
McCoy said: "I went to see my sports medicine specialist Julian Widdowson as I am very sore having aggravated an old injury at Exeter on Tuesday.
"It has been decided it needs some time and it will probably be two weeks before I go back and see him."
McCoy tumbled from Keep Presenting in a maiden hurdle, after which he received oxygen but was able to walk back to the track's medical room for treatment and later headed to hospital for x-rays.
He returned to action the following week, but was stood down at Wetherby with a suspected collarbone injury and subsequently took a few days off.
McCoy had been in flying form through the summer and autumn with the aim of riding 300 winners this season not considered beyond him.
But that magnificent milestone will now be a whole lot harder to achieve.
Meanwhile, star apprentice jockey Cam Hardie spent a second night in hospital following a fall at Kempton on Wednesday evening.
X-rays on the youngster's wrist and elbow revealed nothing was broken, but as a precaution Hardie will have a CT scan on his wrist as he has been suffering from pins and needles.
Hardie is in St George's Hospital, Tooting, after parting company with Dark Tsarina, who clipped heels two furlongs out in a mile-and-a-half handicap.
"The X-rays have shown no breakages in his arm, but because he's got pins and needles in his wrist they are going to do a CT scan, just to make sure and double check. It might be nerve damage," said Hardie's agent Tony Hind.