Inter Milan closed to within a point of Serie A leaders Napoli on Monday after beating Fiorentina 2-1 and gaining revenge for last week's thumping in Florence.
Marko Arnautovic nodded home the decisive goal shortly after halftime at the San Siro to pile pressure on Napoli who could only draw with Udinese on Sunday night.
Champions Inter travel to Turin for a grudge match with Juventus next weekend while Napoli face a tough task at fourth-placed Lazio as a tight title race hots up.
Atalanta are not out of the equation as they sit a further four points back in third following a 5-0 hammering of Verona on Saturday.
Monday's win was Inter's payback for being soundly beaten 3-0 by Fiorentina on Thursday, when the two teams finished a fixture which was stopped in December for Edoardo Bove's heart attack.
Fiorentina are sixth and three points behind Lazio after a match which threatened to boil over following Marin Pongracic's own goal which gave Inter the lead in the 28th minute.
Coaches Simone Inzaghi and Raffaele Palladino were both booked as Fiorentina raged against the decision to give the corner from which Pongracic diverted into his own net.
The corner was given even though Alessandro Bastoni's cleared cross had clearly come from beyond the touchline, with the Viola first left flummoxed at that call and then a goal down.
Inter had been dominant however, and by that point had already hit the woodwork through Lautaro Martinez and Carlos Augusto at two previous corners, while Nicolo Barella went close with an outrageous bicycle kick.
And a big decision did go Fiorentina's way in the 43rd minute when Matteo Darmian inadvertantly handled an inswinging cross and conceded, after a long VAR check, the spot-kick from which Rolando Mandragora levelled the scores.
Inter started the second half exactly as they did the first and were deservedly back in front six minutes after the restart thanks to Arnautovic glancing home Carlos Augusto's floated cross.
That was enough for Inter who continued to create but failed to make the scoreline match a convincing performance against spirited Fiorentina.