Wentworth - England's Matt Wallace believes his decision to change caddie is already paying dividends after shooting to the top of the leaderboard at the BMW PGA Championship at Wentworth on Thursday with a flawless opening 65.
Wallace carded an eagle and five birdies to enjoy a one-shot lead on seven-under par from Henrik Stenson and Jon Rahm, with Justin Rose just a shot further back.
However, it was a nightmare start for Rory McIlroy's pursuit of the world number one ranking as the Northern Irishman finished the day four-over par after dropping five shots on the back nine.
Wallace was heavily criticised for berating his former bagman Dave McNeilly, 67, towards the end of June's BMW International Open, where the defending champion twice found water on the 72nd hole as he chased a birdie to force a play-off.
The two initially made amends with McNeilly back on the bag for Wallace at the Open Championship, before parting ways last month.
"I hope I don't have to make any decisions ever like that again, but it's a business and it's what everyone keeps telling me," said Wallace.
"There are plenty of guys out here who sacked many a caddie and this is my first one. I wouldn't say it was a sacking, it was a parting of ways.
"Sometimes you need to make those hard decisions to go forward. I felt like it was the right one and it is producing some good stuff at the moment."
Rose's participation had been in doubt after he injured his left knee in a slip at home, but the world number four birdied four of his last eight holes to card an opening 67.
"On Monday I went for a scan and I didn't know if I had torn my meniscus or ACL," Rose said. "But there's no ligament damage, it's just a strain and some bruising so I feel quite lucky."
McIlroy was not so fortunate as he blanked reporters after a terrible finish to his round of 76.
After three dropped shots in a row from the eighth, the world number two stopped the rot with a birdie on the par-five 12th but then bogeyed the 13th and 15th and ran up a double-bogey seven on the 17th after pulling his drive out of bounds.
Another wild drive followed on the last and led to a closing bogey, putting his participation over the weekend in danger.
Leading first round scores from the EPGA BMW PGA Championship at Wentworth on Thursday (par 72):
65 - Matt Wallace (ENG)
66 - Jon Rahm (ESP), Henrik Stenson (SWE)
67 - Justin Rose (ENG)
68 - Andrea Pavan (ITA), Joost Luiten (NED), Christiaan Bezuidenhout (RSA), Ernie Els (RSA), George Coetzee (RSA), Sebastian Soderberg (SWE), Paul Casey (ENG), Danny Willett (ENG), Scott Jamieson (SCO)
69 - Alvaro Quiros (ESP), Rafael Cabrera Bello (ESP), Miguel Angel Jimenez (ESP), Romain Langasque (FRA), Julien Guerrier (FRA), Francesco Molinari (ITA), Viktor Hovland (NOR), Alexander Noren (SWE), Steven Brown (ENG), Jordan Smith (ENG), Andrew Johnston (ENG), Robert MacIntyre (SCO), Russell Knox (SCO)
70 - Matthias Schwab (AUT), Gonzalo Fernandez-Castano (ESP), Michael Lorenzo-Vera (FRA), Martin Kaymer (GER), Erik Van Rooyen (RSA), Justin Walters (RSA), Marcus Kinhult (SWE), Joakim Lagergren (SWE), Patrick Reed (USA), Tony Finau (USA), Paul Waring (ENG), Tommy Fleetwood (ENG), Ashley Chesters (ENG), Ross Fisher (ENG), Chris Wood (ENG)
76 - Rory McIlroy (NIR)
79 - Eddie Pepperell (ENG)