Bologna got their first win of the season after firing Sinisa Mihajlovic, as Musa Barrow and Marko Arnautovic overturned the Lucas Martinez-Quarta opener to doom Fiorentina.
The Rossoblu were in turmoil after sacking coach Mihajlovic, a very unpopular decision amongst the fans after three-and-a-half years together and a rapport that became stronger during his leukaemia treatment. New boss Thiago Motta was in the stands, but Luca Vigiani was on the bench as caretaker.
Adama Soumaoro, Nicolas Dominguez and Nicola Sansone were out of action, while Fiorentina missed Nico Gonzalez, Alfred Duncan, Nikola Milenkovic and Gaetano Castrovilli. Confidence was low following the 1-1 Conference League draw with RFS Riga.
Lucas Martinez-Quarta made the decisive block on a Roberto Soriano counter-attack, while Giacomo Bonaventura fired over after sending Michel Aebischer to ground with a dummy.
Lukasz Skorupski flew to fingertip a Martinez-Quarta header over the bar and Dodo was stretchered off on the stroke of half-time with what appeared to be a serious calf strain.
Christian Kouame dribbled past two in the box only to see the finish charged down by Jhon Lucumi.
Fiorentina took the lead after a corner fell to substitute Riccardo Saponara, who juggled it past Stefan Posch and rolled across the face of goal, past Luka Jovic and Skorupski, ready for Martinez-Quarta to come sliding in.
Bologna equalised when Arnautovic hooked the ball back over his head at the touchline and Igor was completely in the wrong position, allowing Musa Barrow to break away and sweep past Pietro Terracciano one-on-one. It was the first goal the Rossoblu scored this season that was not from Arnautovic.
Moments later, Bologna turned the game around completely with Denso Kasius robbing Martinez-Quarta and rolling a ball across the face of goal for Arnautovic to meet at the far post. There was controversy, as Kasius caught Martinez-Quarta on the back of the head with an elbow, but VAR after a long evaluation opted not to suggest an on-field review.
Arnautovic threatened again when acrobatically trying to flick a Soriano assist, but Terracciano got a hand to it and the centre-forward pulled up clutching his hamstring.
Gary Medel bravely charged down a Bonaventura volley with his face, while Terracciano smothered at the feet of Riccardo Orsolini and Barrow curled just wide.
Igor saw red deep into stoppages for his second yellow card, a late lunge on Lorenzo De Silvestri.
Bologna 2-1 Fiorentina
Martinez-Quarta 54 (F), Barrow 59 (B), Arnautovic 62 (B)
Sent off: Igor 96 (F)