Juventus have it all to do in the second half if they want to avoid defeat at Sassuolo, as the hosts head into the break with a 1-0 lead and a numerical advantage.
Chances were at a premium in the opening stages but Juve caused the hosts some problems in the 15th minute when Paulo Dybala's menacing cross caused panic in the penalty area before being scrambled clear.
The Old Lady were left stunned in the 20th minute when Sassuolo took the lead straight from a free kick, Nicola Sansone bending a strike into the top corner to break the stalemate.
Paul Pogba almost levelled things up in the 26th minute when he was picked out by Stefano Sturaro. The Frenchman's shot looked destined for the top corner, but Stefano Sturaro produced acrobatics to keep it out.
Juventus struggled to create chances during the first half, and things could be more difficult for them in the second as they were reduced to 10 men in the 39th minute when Giorgio Chiellini was shown a second yellow card for a clumsy challenge.