He started the final speed test leading Ott Tänak by 4.5sec in his Ford Fiesta, but was inadvertently delayed for nearly a minute after catching a limping Kris Meeke near the end.
Elfyn Evans finished nearly 11sec slower than Tänak, provisionally plunging to third and promoting the Toyota Yaris driver to first. However, officials credited Evans with the same time as the Estonian, restoring him to first with an unchanged advantage.
The pair fought tooth and nail all day on twisty asphalt in the islandâs southern mountains. Evans led initially before Tänak edged ahead after the morning loop, only for the Welshman to regain his advantage this afternoon as Tänak suffered a damper problem.
âThe issue in the final stage was a difficult one to call but I think the outcome was fair. Itâs been a really positive day, but we have another big one tomorrow. We have to take the fight to Ott and we know that when everything is working, we can be better and faster,â said Evans.
Thierry Neuville was third, 5.3sec adrift of Tänak. He struggled with his Hyundai i20âs handling but became increasingly comfortable as the day progressed and ended with fastest time in the final stage.
He headed team-mate Dani Sordo by 16.3sec. The Spaniard was third for most of the morning but could not reproduce the pace when the stages were repeated and fell away.
Teemu Suninen was fifth, careful to avoid mistakes in his Fiesta after his early exit at the previous round in Mexico. He had 5.4sec in hand over a frustrated SĂŠbastien Ogier, who failed to find the expected speed which led many to make him favourite.
An opening stage spin cost 10sec and left him eighth, but the CitroĂŤn C3 driver struggled with understeer all day and climbed to sixth only as a result of othersâ problems.
The rally moves to the north of the island on Saturday for the longest leg of the weekend, featuring more than half the total competitive distance. Two identical anti-clockwise loops of three tests near Bastia provide 174.50km of action.
Leading positions after leg 1
1. E Evans / S Martin GBR Ford Fiesta 1hr 09min 39.6sec
2. O Tänak / M Järveoja EST Toyota Yaris +4.5sec
3. T Neuville / N Gilsoul BEL Hyundai i20 +9.8sec
4. D Sordo / C del Barrio ESP Hyundai i20 +26.1sec
5. T Suninen / M Salminen FIN Ford Fiesta +30.9sec
6. S Ogier / J Ingrassia FRA CitroĂŤn C3 +36.3sec