Sarri concedes he's missed working in the Premier League.
The former Lazio and Napoli coach told Sky Italia: “That was the most fundamental error in my career,.
“We had everything required to remain, it’s a difficult club to work at where you probably don’t get to finish the second season, as practically nobody did in the Roman Abramovich era.
“At least I would’ve remained in the general Premier League situation. We had a good journey there, as the previous season the team finished fifth, then we were third behind Liverpool and Manchester City, who were above all the rest.
“We won the Europa League with 13 victories and lost the Carabao Cup Final on penalties to Manchester City, after eliminating Liverpool and Tottenham, who that year had reached the Champions League Final.
“I made an enormous error that I should’ve avoided. The desire to return to Italy should’ve been inferior to the desire to stay in the Premier League, but that was not the case.”