Bologna held on for a scoreless draw to end champions Juventus’s 15-match winning streak in Serie A on Friday.
The Old Lady of Turin had not failed to win in the league since a 1-0 reverse at Sassuolo at the end of October and turned an 11-point gap to the top of the table into a one-point advantage over Napoli with a 1-0 success against their nearest rivals last weekend.
However, Juve travelled to a Bologna side who were themselves in the midst of a resurgence since former Italy coach Roberto Donadoni took over the reins in October after Delio Rossi was sacked.
Bologna were 18th then and have since risen to ninth.
Already a week ago, Juve showed signs of tiredness despite beating Napoli and their efforts seemed to catch up with them in Bologna.
Coach Massimiliano Allegri will be especially concerned with Juve hosting Bayern Munich in the Champions League last 16, first leg on Tuesday.
The champions, seeking a fifth straight Scudetto crown, could even lose top spot if Napoli beat AC Milan at home on Monday night.
Juve missed the attacking threat of Paulo Dybala, who only came on as a substitute late on, and lacked ideas going forward.
They failed to get a single shot on target in the opening period but turned up the heat late on when France midfielder Paul Pogba and Alvaro Morata both went close in the final six minutes.