The deficit is four with four days to go as title chaser William Buick fired in a 96-1 treble at Leicester on Tuesday to keep alive his hopes of a first UK championship.
Success on Parlando, Kentucky Kitten and Rhythm N Rock were the highlights of eight rides for Buick, who also partnered three seconds, while Murphy struck on one of his four mounts, Able Kane, in the feature 7f handicap.
Paddy Power cut Buick, booked for eight rides at Nottingham on Wednesday, to 7-4 (from 2-1), with Murphy, who has six chances to boost his tally on the same card, out to 4-9 favourite (from 4-11).
A fitting finale saw Buick's mount Rhythm N Rock, trained by John Butler, mow down Murphy's odds-on favourite Future King in the 7f novice, met with cheers from backers among the midweek crowd.
'I've got to keep kicking'
After sealing the treble, Buick said: "It's been a good day and I have lots of rides to come over the final four days. I've got to keep kicking and see where it takes me."
Able Kane's success took trainer Rod Millman's tally to 35 winners, ensuring it is his best season since 2009, and once again proving an important ally for Murphy with the combination enjoying 11 winners this term.
Murphy, whose uncle Jim Culloty was cheering him home on track, said: "Able Kane is genuine and has been well placed. Fair play to Rod as he's had a marvellous season and his sons James and Pat play a big part too."
Asked if he was able to enjoy the title race coming down to the final few days, Murphy said: "I've never enjoyed it when it's like this! I'll do my best and that's all you can do."
Parlando's victory for Buick in division two of the 7f novice took Charlie Appleby's fantastic juvenile record in Britain this year to 35 winners and 93 first-four finishers from 116 runners, while Kentucky Kingdom was Buick's first winner on just his second ride for Tim Easterby in the 1m2f handicap.
Buick said: "It was a really nice performance from Parlando on debut, it's pretty soft ground out there but he saw it out well to the line.
"It was very straightforward on Kentucky Kitten – he loved that ground and stays very well."
Both jockeys head to Nottingham with a handful of live chances in the eight-race afternoon fixture.
Buick will be hoping to strike with Medyaf and Rockfire, who are at the head of the market in the opening two races and could deliver an early advantage before Murphy has his first ride of the day.
Murphy may miss the first two races but he holds prominent chances in the final six, starting with Candy Kitchen, who was beaten a neck last time at Thirsk, in the 1m½f fillies' maiden (2.05).
Legendary Day, who has won under both Murphy and Buick this season, steps up to 1m2f for the first time (3.15) for the champion jockey but will face a challenge against the ultra-consistent Fairmac for his title rival.
Things may come to a head between the pair in the 5f handicap (4.25) with Buick's mount Raasel and the Murphy-ridden Natural Path both chasing hat-tricks.
Buick will aim to cap off Wednesday with another winner in the final race of the day (4.55) on the Michael Appleby-trained Mehmo.
Treble for William Buick!— Racing TV (@RacingTV) October 12, 2021
He gets the better of Oisin Murphy in the finale as Rhythm And Rock strikes at 5/1 for John Butler at @LeicesterRaces.
The gap is now four in the title race... pic.twitter.com/h5XiceZz34