The Finn, driving a Hyundai i20 R5, had ended the opening day 27.0sec back from top spot. The gap remained similar for much of Saturday morning as he and Østberg traded times, but a non-competitive mishap for his rival handed him the lead.
On the liaison section back to mid-leg service, a bolt came out of the cross-member of Østberg’s Citroën C3 R5, causing a wheel to fall off. He repaired the car at the roadside, but received a 1min penalty after arriving to service 6min later than his scheduled time.
Huttunen was unable to match Østberg’s pace over the second half of the day. He dropped a handful of seconds on each stage and his lead was sliced to just 2.7sec at close of play.
"I think I have to push tomorrow if I want to win, but let's see. It's also important to take the points, because in Finland we retired," he said.
Defending champion Østberg was confident he would be able to catch the leader over Sunday’s shorter leg, but admitted he was exhausted after a tough day.
"I have used all my power today to repair the car many times and also to drive as fast as possible. It's been a very demanding day, but we are within striking distance, that's for sure," he mused.
Škoda Fabia Rally2 star Marco Bulacia ended the day 2min 00.8sec behind Østberg in third. A spin in Sedini - Castelsardo cost a handful of seconds, but the Bolivian youngster was happy with his progress in terms of car set-up and pace notes.
Sardinia regular Martin Prokop was a further 5min 01.5sec further back in an M-Sport Ford Fiesta Rally2 machine, whilst Enrico Brazzoli trailed the leaders by 25min 23.3sec to round out the top five in a Fabia.
Adrien Fourmaux restarted after beaching his Fiesta on Friday. The Frenchman managed to bag two fastest times and ended over one hour off the pace in sixth.
Georg Linnamäe retired his Polo in SS10, whilst Sean Johnston and Andreas Mikkelsen failed to restart after issues on Friday.
- Full coverage from Rally Italia Sardegna is available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.