Fiorentina's title bid suffered a wobble as they were held to a 1-1 draw at Sassuolo.
The visitors would have gone top of Serie A -- albeit for a couple of hours -- had they won the early kick-off, and they looked on course when Borja Valero fired them into an early lead.
But Sergio Floccari headed Sassuolo level before half-time and Fiorentina could not find a winner after the break.
Fiorentina already had two decent penalty appeals -- for handball and a foul on Josip Ilicic -- turned down before they took a fifth-minute lead.
Ilicic's low cross was missed by Giuseppe Rossi but Valero dug the ball out from under his feet to fire home from eight yards.
Valero was almost gifted a second when a poor clearance from Andrea Consigli fell to him 20 yards out, but the Sassuolo keeper was able to scramble back into his goal in time to collect the shot.
Consigli redeemed himself with a fine save from Ilicic after the winger was sent through one-on-one.
And four minutes before the break Sassuolo hauled themselves level when Floccari towered above three defenders to nod Sime Vrsaljko's floated cross past Fiorentina keeper Ciprian Tatarusanu.
The visitors came close to getting their noses in front again when Manuel Pasqual fizzed a shot across goal, but Consigli got a vital touch to palm the ball clear.
Consigli also kept out a late curler from Ilicic to ensure Fiorentina were left frustrated.