Mikkelsen began the final day of the Intercontinental Rally Challenge event leading by 4.5s but now trails his fellow ŠKODA Fabia Super 2000 driver by 0.8s with three stages remaining.
Unconfirmed reports suggested Mikkelsen suffered an impact on the stage although the Norwegian insisted he was just too cautious through test, which he said was “very slippery”.
Giandomenico Basso set a rapid pace through the stage in his M-Sport Ford Fiesta RRC run by the Italian A-Style Team to go fastest of all, 6.2s quicker than Kopecký. Basso is now just 2.7s off the overall lead.
"We are trying to push to the maximum,” said the Italian.
Paolo Andreucci was third fastest for Peugeot Italia as he looks to get back ahead of Italian championship rival Umberto Scandola, who was 1.4s slower than the six-time Targa Florio winner.
The Cefalú stage was last used in its current 18.00-kilometre configuration in 2009.
The stage runs downhill into a valley before an uphill finish. Its close proximity to the town of Cefalú, a popular Sicilian holiday resort, ensures huge numbers of fans line the route.