Sassuolo were denied the chance to claim back-to-back Serie A victories for the first time in their history as Cagliari rallied from two goals down to force a draw at the Stadio Sant'Elia.
The Serie B champions, who were roundly punished throughout their torrid introduction to top-flight football, have since escaped the bottom three with a run of two victories from three games and looked set to win again when Lino Marzorati and Simone Zaza scored during the first half in Sardinia.
The Neroverde are, however, yet to fully shake their naivety at this level and crumbled after the break. Goals from Nene and Marco Sau rescued a 2-2 draw for Cagliari, who would have dropped below their opponents in the table with a second home defeat of the season.
In what was a first-ever Serie A meeting between the two clubs, the mainlanders enjoyed the first shot on goal with Zaza trying to surprise Vlada Avramov from distance.
Cagliari midfielder Radja Nainggolan then unleashed a powerful right-footed drive from outside the box that clipped a post and bounced wide.
Sassuolo pushed back and opened the scoring in the 14th minute.
Defender Marzorati was all alone in the Rossoblu area at a corner and had plenty of time to beat the stranded Avramov with a header.
The visitors would double their lead through Zaza five minutes later.
The former Sampdoria striker fired a warning shot moments before finding the back of the net and his next effort was unstoppable for Avramov as he picked up a through-ball from Gaetano Masucci to blast home with an angled drive.
With Cagliari on the ropes, Zaza very nearly scored a quickfire third after robbing Davide Astori of possession in a dangerous area, but he could not find the target.
Halving the deficit before the break would have raised the Sardinians' spirits but, despite the best efforts of Nainggolan, his deflected strike veered wide of the mark to set up 15 minutes of soul-searching in the dressing room.
Nene clearly listened to Diego Lopez's half-time team talk as he streaked onto the edge of the area to blast at Gianluca Pegolo with a deceptive right-footed drive.
Indeed, Cagliari were much livelier and managed to ensure the game would be a contest for its final 15 minutes as their Brazilian striker beat Pegolo to his far post with a firm header from Francesco Pisano's cross.
Nainggolan had been a constant thorn in Sassuolo's side all day and seemed fated to have a decisive impact before the final whistle.
The Belgian midfielder did produce the shot that settled the tie but it fell to Sau to race onto the loose ball and tap home after Pegolo had got gloves to the original strike.