Genoa 3 - 1 Juventus: Giovanni Simeone at the double as Juventus are beaten by Genoa

Giovanni Simeone scored twice as Genoa inflicted a convincing 3-1 defeat on reigning champions and Serie A leaders Juventus.

The Argentinian son of Atletico Madrid boss Diego caught Massimiliano Allegri's Scudetto hopefuls cold with a third-minute opener before cutting through a sleepy back-line to double the Grifone lead.

As the Bianconeri scrambled to try and rescue a point, Brazilian midfielder Alex Sandro scored an unfortunate own goal to put a share of the points out of reach, with Miralem Pjanic's late strike from a free-kick merely sparing the Turin club from their worst league reverse since January 2011.

Following AC Milan's big win at Empoli on Saturday night, the Old Lady are four points clear at the top ahead of next weekend's meeting with form team Atalanta, who are now joint third having won six games in a row.

Juve's 3-1 Champions League victory at Sevilla in midweek took a lot out of the players and Allegri shuffled his pack accordingly.

He will not have anticipated the effect his changes might have, however, with a new-look defence failing to communicate from kick-off, bringing disastrous consequences.

Inside three minutes Leonardo Bonucci's poor mistake allowed Luca Rigoni and then Lucas Ocampos to take free shots at Gianluigi Buffon. After the veteran goalkeeper had pulled off a desperate double save, Simeone swept in for an easy finish.

The Bianconeri did not heed the warning and 10 minutes later Danko Lazovic skipped past the sleepwalking Sandro to pick out Simeone for a powerful header past the infuriated Buffon.

Rigoni missed the chance to make it 3-0 when smashing Diego Laxalt's cross wide but Genoa would not wait long for another goal.

Sandro's afternoon went from bad to worse as he made a hash of clearing Rigoni's snapshot away from danger, instead diverting the ball into his own net.

Whatever was said over the break inspired Juve at least a little as Pjanic was soon found rampaging forward to stick Mario Mandzukic's backheeled pass just wide.

Genoa were not worried and bit back with Simeone carving out a one-on-one opportunity with Buffon - the Italy keeper managed to hypnotise the youngster.

Try as they might Juve could not find a way through and to add insult to injury they were reduced to 10 men when, with a little over 10 minutes remaining, full-back Dani Alves was forced off the pitch when all three visiting substitutions had already been made.

What was required to ease the pain was a set-piece and a free shot at goal, which Pjanic gleefully took in the 82nd minute, his free-kick soaring over the wall and over Mattia Perin's outstretched fists.