With eight Serie A wins and two in the Champions League Juve were all set to extend that fine run when Ronaldo put Massimiliano Allegri's men into a first-half lead.

But Juve were made to pay for failing to convert a hatful of chances when Daniel Bessa headed in a second-half equaliser.

Ronaldo, despite the turmoil of explosive rape allegations that surfaced before the international break, notched up his fifth goal for his new employers since his headline move from Real Madrid in the 18th minute, ironically helped by a mistake from Genoa's top-scoring Polish striker Krzysztof Piatek.

A communications mix-up saw Piatek leave Joao Cancelo's blocked shot for his keeper, but the loose ball fell at Ronaldo's feet and he tapped in to an empty net.

This was the 33-year-old's 400th career goal in Europe's top five leagues, making him the first player to reach that tally.

Lionel Messi is next best on 389.

Ronaldo, who returns to Old Trafford on Tuesday to face his old club Manchester United, would have bagged a double shortly after but his low shot was denied by Genoa keeper Ionut Radu's diving save.

With Genoa struggling to contain the lively Cancelo down the right Juve were firmly in control, their only regret at the break being they weren't further in front.

Genoa had to wait until the 53rd minute for their first shot on target, and unsurprisingly it fell to Piatek, but his hopes of swelling his nine-goal Serie A haul were dashed when Juve keeper Wojciech Szczesny tipped his shot around the post.

Energised, the 23-year-old should have levelled seconds later, outjumping Leonardo Bonucci but his header went wide.

In an attempt to stifle Genoa as they scented an equaliser Allegri replaced Juan Cuadrado with Douglas Costa, the Brazilian winger making his first appearance since a four-game ban for spitting.

Juve paid heavily for failing to kill off the encounter when Bessa headed a cross from Christian Kouame into the back of the net on 67 minutes.

Allegri responded by introducing Paulo Dybala for Blaise Matudi as a frantic finale beckoned with Genoa holding on for a surprising point.

Napoli cut the gap on Juventus to four points with a third successive win in all competitions and a third clean sheet in a row after a 3-0 win at Udinese.

Napoli, coached by Carlo Ancelotti who will take his side to former club Paris Saint-Germain in the Champions League in midweek, were in front after 12 minutes on Saturday through a superb effort from Spanish player Fabian Ruiz.

Despite dominating the game, Napoli had to wait until the last 10 minutes to wrap up the points thanks to a Dries Mertens penalty and a strike from Croatian midfielder Marko Rog.

Earlier, Roma came unstuck 2-0 to visiting minnows SPAL to dash their hopes of a fourth straight league win.

The hosts had beaten Frosinone, Empoli and above all city rivals Lazio and had been hoping to improve on their sixth place in Serie A ahead of Tuesday's home Champions League game with CSKA Moscow.

SPAL, who came a highly respectable 13th in Serie A following promotion last season, went ahead with a slickly-converted Andrea Petagna spot-kick on 38 minutes.

A flashing header from Kevin Bonifazi finished off a corner on 56 minutes to make it 2-0 to the visitors for their fourth win in nine matches, losing their other five.