Juventus coach Massimiliano Allegri says he expected his team to find it difficult against lowly Frosinone after they laboured to an unconvincing 2-0 win.

The Serie A champions required late goals from Cristiano Ronaldo and substitute Federico Bernardeschi to scrape past a team who have so far failed to score a goal this season.

Victory at Stadio Benito Stirpe maintained Juve's 100 per cent start to the campaign and followed a difficult midweek Champions League trip to Valencia in which they played most of the match with 10 men due to Ronaldo's red card.

"We were expecting a game like that," Allegri told Juventus' offical website.

"We came into this match having played with 10 men for 70 minutes in midweek and it was one of those games that become really tricky if you don't find an early breakthrough.

"I'm happy with the way the lads kept working the ball towards Frosinone's area quickly and calmly.

"Eventually the goal came for us."

Ronaldo, who had a number of chances to open the scoring, eventually did so when he scuffed home a first-time effort after Miralem Pjanic's blocked shot fell into his path.

It was the Portuguese forward's third goal since moving from Real Madrid after his brace in last week's win over Sassuolo.

The hosts, promoted last season, had been roared on by a passionate and vocal home support and, as they pushed for an equaliser, substitute Bernardeschi added a second on the counter attack deep into added time.

Allegri admitted the first-half performance was below par and was impressed with Bernardeschi's cameo appearance.

"We struggled in the first half because we were channelling our play down one flank," the 51-year-old added.

"We did better in the second half when we pushed Emre Can and Pjanic further forward.

"Bernardeschi was excellent when he came on. With Emre in front of the defence you can afford the luxury of having more skilful midfielders."

Sunday's late drama means the Bianconeri retain their three-point lead at the top of the table after five games.

They host a midweek clash with Bologna before second-placed Napoli –  who won 3-1 at Torino on Sunday – travel to Allianz Stadium next week.

"I expected Napoli to be up near the top, although they have lost a game," Allegri added.

"We have a chance to put some daylight between us and the pack but first of all let's make sure we go into the head to head with Napoli top of the table."