Frenchman Sebastian Loeb boosted his hopes of a fourth straight world rally title after championship leader Marcus Gronholm crashed out in Japan.
Gronholm driving in Japan shortly before his crash
Loeb can overtake Gronholm in the drivers' standings if he finishes fourth or higher in Japan.
And he ended a wet opening day second behind Finn Mikko Hirvonen's Ford.
Gronholm's hopes suffered when he lost control of his Ford at a fast left turn during the fourth stage, sliding down a bank before crashing into a tree stump.
Even if mechanics can repair the damage to the roll-cage inside the driver's door before Saturday's second leg, the time penalties for missing six stages would leave the Finn way back.
"I slid wide and my right rear wheel hit some straw bales," Gronholm said.
"The stage was covered with loose gravel and it was slippery throughout. It will be hard to repair."
Loeb had reduced the gap in the Championship race to four points with back-to-back wins in Catalunya and Corsica and the Citroen driver set the pace in the morning in Hokkaido.
But Hirvonen will take a significant lead of 10.3 seconds over the triple world champion into leg two with Finland's Jari-Matti Latvala third for Ford a further 3.4 seconds back.
Victory for Loeb in Japan would give him a six-point advantage over Gronholm heading to the penultimate round in Ireland next month.