Cristiano Ronaldo got his 2020 up and running with a hat-trick as Ragnar Klavan's error helped gift Juventus a 4-0 win over Cagliari, sending the champions back above Inter at the Serie A summit.

Despite a dominant first-half display, Juve - who were defeated by Lazio in the Supercoppa Italiana in their final match of 2019 - were unable to find a way through before Klavan's calamity.

But once presented with a clear chance, Ronaldo made no mistake, keeping his composure to beat Robin Olsen, who was beaten again by the former Real Madrid star from the spot in the 67th minute.

Ronaldo's penalty came after Giovanni Simeone almost snatched an equaliser against the run of play, but a strike from substitute Gonzalo Higuain and a composed third from Ronaldo comfortably ensured Juve made it 30 consecutive home league matches without defeat.