The Finn was in a league of his own winning all three stages in the Greek mountains as he transformed a 3.7s overnight lead into a 21.4s advantage over Hyundai’s Ott Tanak.
Toyota’s Rovanpera produced a masterclass display barring a lucky escape on the final morning stage when he clipped a bank at high speed.
Championship leader Sebastien Ogier started the day 3.9s adrift of the lead in third, but now finds himself 36.8s behind, such was Rovanpera’s pace.
Hyundai’s Dani Sordo remained fourth overall 1m15.8s back, but ahead of M-Sport Ford duo Adrien Fourmaux and Gus Greensmith as the morning came to a close.
After Friday’s mechanical dramas Elfyn Evans and Thierry Neuville climbed the leaderboard to the fringes of the top 10 in ninth and 12th positions, with the pair 5m28.9s and 7m23.4s in arrears respectively.
Rovanpera came out the blocks fast, blitzing the opening (24.25km) stage of the day with a drive similar to his performance in July’s Rally Estonia where he stamped his authority on the event on the Saturday morning.
The stage, held at much higher altitude, featured sizeable sections of damp gravel from the week’s earlier rain, that were described as like “driving on ice”. It was also the stage that was covered in fog on the recce which hampered crews as they made their pace notes.
The conditions failed to hamper the Toyota driver as he won the stage by 5.6s from his nearest rival Tanak, with the Finn an impressive 12.8s faster than Ogier.
“It was pretty damp in this one. The ideal choice would be full softs [tyres] in there for sure, but we don’t have many for the rally, so that’s the bigger question,” said Ogier.
Toyota teammate Evans was third fastest on the stage now equipped with a fully functioning gearbox in his Yaris. Neuville, who also suffered mechanical issues on Friday, enjoyed a trouble-free run but was 24.4s adrift of the pace on hard tyres.
Rovanpera continued to apply pressure on his rivals after dominating Stage 8 to extend his overall lead even further.
This time an inspired tyre call (three hards, three softs) helped him take a further 7.6s out of Tanak and 13.9s faster than Ogier as the majority of the runners struggled to find grip on the slippery gravel.
“I am feeling good. It was a nice tyre choice, so thanks to my engineer also because he was supporting me,” said Rovanpera.
“It was a really difficult two stages – like now when I had the hards on the front, in the mud it was tricky, but I was pushing to try and gain everything I could in the other places.”
Fourmaux found out just how little grip there was coming down a mountain side road as he found an armco barrier on one of several hairpins. Luckily the damage to the front right was only cosmetic and the Frenchman reached the finish.
“I went straight in a barrier in a slow corner, It was quite tight and I just lost the grip,” said Fourmaux. “It probably is the same for everybody, but it was really difficult to drive – there is no grip.”
Rovanpera couldn’t be stopped on the final stage of the loop as he took another 4.6s out of nearest rival Tanak, who was second quickest on the stage, ahead of Ogier, the same order as the previous tests.
However, the rally leader admitted he was lucky to escape high speed run in with a bank.
“The moment was a huge one,” said Rovanpera. “I have to say we were lucky to escape and that there was nothing in the ditch. It was maybe a bit too much from the pace notes, I was pushing a bit too much. I tried to be a bit more careful after that.”
Rovanpera wasn’t the only driver to have a moment as Greensmith spun his Fiesta at a hairpin, but continued unabated.
Crews will tackle three more stages this afternoon, including a repeat of the morning’s first stage, to conclude Saturday’s running at the Acropolis Rally.