Inter Milan again wasted the chance to retain their Serie A title when they were held 2-2 at home by Siena on Sunday with Marco Materazzi having a penalty saved.
Second-placed AS Roma beat Atalanta 2-1 to cut the gap to one point with one round of matches remaining next weekend in an exhilarating finish to the season.
Inter, who lost to AC Milan last Sunday to spurn their first opportunity of sealing the scudetto, visit relegation-threatened Parma and Roma go to Catania, who could also go down.
Bottom side Livorno were relegated after a 1-0 defeat at home to Torino while Empoli must beat Livorno next Sunday to have any chance of staying up after losing 2-0 at Reggina, who are now safe.
Third bottom Parma and fourth bottom Catania will have everything to fight for next Sunday with two points separating the teams.
Fiorentina came from behind to beat Parma 3-1 to move into fourth spot and the final Champions League qualifying place after AC Milan, now two points behind with a game left, lost 3-1 at Napoli.
Catania were safe with a minute to go in their game at third-placed Juventus before Alessandro Del Piero snatched a 1-1 for the hosts.
Inter looked to cruising to the title after just 11 minutes when Patrick Vieira headed in a corner after sustained pressure.
However, Massimo Maccarone swept in at the near post to equalise for Siena, who had nothing to play for after sealing their Serie A place last weekend.
Inter's 17-year-old striker Mario Balotelli sent a packed San Siro crazy when he nodded in on halftime but Houssine Kharja, a former Roma player, brought Siena level again in the second half with a neat finish from the edGe of the area.
The drama was far from over at 2-2 with Materazzi's nervous penalty well-saved by Alex Manninger 12 minutes from time.
Roma, 11 points behind Inter in February, overcame Atalanta thanks to Christian Panucci's header and Daniele De Rossi's free kick.
If Luciano Spalletti's side win next weekend and Inter fail to take three points they will snatch the most unlikely of titles. However, if Roma draw and Inter lose, Mancini's team will be champions because of their better head-to-head record over Roma.