The Serie A champions had been held by Parma last week, despite the Portugese forward’s double.

Now they have left second-placed Napoli trailing, after Carlo Ancelotti’s side were held to a goalless draw at Fiorentina on Saturday.

Paulo Dybala again started on the bench, coming on late for the champions to help set up the third goal, with coach Massimiliano Allegri saying he needed to find the right balance.

“Ronaldo and Dybala can certainly play together and they will do, but we need everyone to work hard in order to keep the team balanced,” said Allegri.

“It all depends on who you are playing against. Sassuolo have a strong midfield, so I had to balance my team that way today.

“Players are disappointed, but every now and then sitting on the bench is necessary to recharge batteries and rediscover the right mental toughness.”

Juventus had started slowly, with goalkeeper Wojciech Szczesny saving twice in the opening minutes as the champions were without injured defenders Leonardo Bonucci and Giorgio Chiellini.

The pair are fighting to be fit for Juventus’s European Champions League last-16 trip to Atletico Madrid in 10 days’ time.

Juventus broke through after Sassuolo goalkeeper Andrea Consigli rushed out to parry a Ronaldo shot, leaving the way clear for Khedira to turn in the rebound after 23 minutes.

It was the German international’s second league goal of his injury-hit campaign, after scoring the opening goal of the Serie A season against Chievo on August 18.

Consigli denied Federico Bernardeschi just before the break, with a Khedira header flying wide.

But Portuguese star Ronaldo jumped highest after 70 minutes to meet Pjanic’s corner for his fourth goal in his last three league games to bring his tally to 20 goals for Juventus in all competitions.

The 34-year-old celebrated by mimicking Dybala’s ‘mask’ goal celebration. 

Argentine Dybala came off the bench seven minutes from time along with Can, and was involved in the build-up for the final goal with Ronaldo proving the assist.

Inter Milan are third – 20 points behind Juventus – after beating Parma 1-0 on Saturday, for their first league win of 2019.

But city rivals AC Milan are just four points behind Inter in fourth after beat struggling Cagliari 3-0, with new signings Lucas Paqueta and Krzysztof Piatek both scoring.

Cagliari defender Luca Ceppitelli gave the hosts their first with an unfortunate own goal after 12 minutes.

Brazilian Paqueta volleyed in the second after 22 minutes, with Polish forward Piatek again finding the net after 62 for his fourth goal in all competitions.

Paqueta dedicated his first goal in Italy to the 10 victims of the fire that ripped through buildings at Rio club Flamengo, where he started his career.

The battle for elite European football remains tight, with Atalanta, Roma and Lazio all just a point behind AC Milan.