Eight-time world champion Ogier started Saturday with a 22.8s lead and the Toyota driver went on to stamp his authority on the event in the afternoon.
However, heavy rain arrived during the day’s final stage, which allowed Rovanpera to cut Ogier’s lead to 16.7s ahead of Sunday’s final six stages.
Toyota’s Elfyn Evans ended the day in 2m23.3s down on Rovanpera in third after leapfrogging team-mate Takamoto Katsuta in the tricky wet conditions in stage 13. Dani Sordo led Hyundai’s charge in fifth (+3m52.3s) after team-mate Esapekka Lappi retired on stage 11 with a mechanical issue.
M-Sport’s Ott Tanak and Pierre-Louis Loubet managed to survive to hold onto sixth and seventh overall, while Thierry Neuville has recovered to ninth after his Friday retirement behind WRC2 leader Kajetan Kajetanowicz.
The afternoon began with Ogier seemingly putting a stop to Rovanpera's Saturday morning charge by claiming his sixth stage win in the 29.32km Soysambu test, which was held in much drier conditions compared to the morning pass.
Ogier was 6.4s faster than nearest rival Rovanpera, but the Frenchman’s run wasn’t completely clean after reaching the stage end with foliage protruding from his GR Yaris.
Rovanpera admitted that he wasn’t pushing in the stage with his main focus on bringing the car to the end of the day, given his title rivals Tanak and Neuville were sitting sixth and 14th respectively.
But the big story from the stage was the demise of Lappi, who pulled off the stage and into retirement with a prop shaft-related issue. The Finn suffered a similar problem in Wednesday’s shakedown.
Lappi's woes handed Evans third overall, although the Welshman was only 2.8s ahead of the chasing Katsuta.
Tanak inherited sixth, but lost 1m30s due to his second wheel change of the event.
Ogier continued his stranglehold of the rally by taking 3.5s from Rovanpera in stage 12, Elmenteita.
"I just try to do my job and not do any mistakes," said Ogier, who was second fastest behind stage winner Katsuta. "Hopefully we stay out of trouble up until the end of the day now."
Katsuta’s first stage win of the event was enough to claim third overall from Evans by a margin of 2.1s, while Rovanpera was resigned to just holding onto second overall.
"Definitely now, with EP [Lappi] also dropped out, there are such big gaps behind and if nothing happens it's impossible to catch Seb by driving," said Rovanpera. "I don't want to take huge risks anymore."
The much-anticipated rain finally arrived as the heavens opened towards the end of the day’s final test (Sleeping Warrior, 31.04km). It created incredibly treacherous conditions as crews skated around on rocky muddy roads, struggling for traction.
The slippery road surface played into Rovanpera’s hands as the Finn deployed his famous wet weather driving skills to take 15.3s out of Ogier’s lead.
"Last year was slippy but nothing like this," said Rovanpera. "Even on the straights, second gear was quite high-speed. We are here in one piece and that was the only goal for today."
Ogier found the going tough in the stage, enduring a wild slide early on, before picking up punctures to both front tyres towards the end.
"I cannot say that I have so much luck with these tyres, but that's the way it is,” said Ogier.
Tanak, Loubet, Neuville and Katsuta all suffered spins as they scrambled for grip, the latter damaged his rear wing in one of his wild moments.
The quartet all survived to reach the stage end but Katsuta lost his grip of third overall. The rally will conclude following six more stages on Sunday.
