Neuville started this penultimate leg 16.0sec back from overnight leader Sébastien Loeb in fourth overall but climbed two positions to take the runner-up spot with a storming run through the monster 33.2km Pyrgos test.
Loeb crossed the flying finish of the opener with an extended advantage of 19.0sec but his rally was thrown into turmoil when his M-Sport Ford Puma’s alternator belt failed on approach to the stop line.
After freewheeling down the road, Loeb and co-driver Isabelle Galmiche attempted to replace the broken belt but ran out of time and retired for the day - leaving Neuville out front as the leaderboard turned on its head.
Also in trouble was Pierre-Louis Loubet, who brought up the rear of M-Sport Ford’s 1-2 on Friday evening. A delaminated tyre at Tarzan cost the Frenchman over one-minute and he plummeted down the standings.
Neuville’s dominant stage win at Tarzan consolidated his position and he arrived back to service in Lamia a whopping 31.0sec clear of the field.
"I am surprised,” Neuville admitted. “We had a good clean run this morning and I think the tyre choice was good as well, but I struggled a bit with the balance at the rear and I had to adapt a bit.
“It's good that we can extend a lead on a loop like this. It gives us confidence for the afternoon but we know there is still a long way to go,” he added.
Esapekka Lappi - driving a Toyota GR Yaris - was Neuville’s closest challenger. He held third overall for most of the morning but leapfrogged Ott Tänak in the final stage as the Estonian complained of a differential fault on his Hyundai. Just 1.3sec splits the pair with three stages remaining today.
Dani Sordo brought his i20 home 12.0sec further back in fourth ahead of Elfyn Evans, who reported mixed grip levels in his Yaris.
Puma cars accounted for the next three positions after M-Sport’s nightmare loop. Gus Greensmith was sixth despite his engine intermittently cutting out and Loubet languished 20.4sec back following the puncture. Craig Breen - who punctured on Friday - completed the trio.
Takamoto Katsuta’s confidence took a knock when he spun in the first stage. The Japanese driver slipped behind Breen to ninth overall, with WRC2 leader Emil Lindholm rounding off the top 10.
Championship leader Kalle Rovanperä is almost 15 minutes adrift of the leaders after sideswiping a tree on a right-hander at Perivoli. The 21-year-old managed to limp back to service with heavy body damage whilst also nursing a brake issue.
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