Vincenzo Montella returned for a second stint as Fiorentina coach on Wednesday after the Serie A club named him as their replacement for Stefano Pioli who quit in acrimonious circumstances on Tuesday.
The 44-year-old was in charge for three seasons between 2012 and 2015 and enjoyed remarkable consistency, leading Fiore to three successive fourth places in Serie A. They also reached the Coppa Italia final and the Europa League semi-finals.
Fiorentina, who are 10th in Serie A and have reached the Coppa Italia semi-finals, announced his appointment on their website and said he had signed a contract until June 2021.
After leaving Fiore, Montella was coach of AC Milan for just under 18 months and Sevilla for four months.
Fiorentina have won only one of their last 11 matches in all competitions and suffered a shock 1-0 defeat at home to second-bottom Frosinone on Sunday.
On Monday, the club issued a statement strongly criticising the team's recent performances but said it wanted Pioli, in charge for one year and 10 months, to lead the recovery.
It asked Pioli to "handle this situation with the competence and seriousness he showed in the first half of the championship."
On Tuesday, Pioli resigned, saying his professional and human abilities had been called into question.
"I have always assumed my responsibilities, I have always guaranteed professionalism, respect and maximum commitment in my work," he added.
The exchange continued on Wednesday as the club issued another statement.
"We consider his attitude incomprehensible and unjustifiable, putting the club in an unexpected situation that is complicated to manage," it said.
"It was a duty to clarify the position of the club and to call for the utmost commitment from everyone without offending or belittling anyone."
Fiorentina routinely finish in the top half of Serie A although they have not won a trophy since the Coppa Italia in 2001 and the last of their two league titles was in 1969.
They showed all their potential in thrashing AS Roma 7-1 in a Coppa Italia quarter-final in January but since then their form has dropped.