Then, having returned to the game nearly 12 months later, he spent much of the next two years battling to win over manager Jose Mourinho as the Portuguese demanded greater professionalism from the former Southampton defender.
Former Arsenal manager Arsene Wenger has resumed his rivalry with Manchester United manager Jose Mourinho after the Frenchman said that the Portuguese tactician was the one responsible for Alexis Sanchez' poor form with the Red Devils.
"I think I knew how important this season was going to be, especially the start of it coming in the previous year of (my contract)", he said. "But I think, also, that you all have to respect him". "Apart from that is another match for me, I want to do well for my team, players, support, I am 100 per-cent Manchester United tomorrow, no more space than respect for the stadium and the fans".
That may be interpreted as implied criticism of Mourinho, but Sarri was not about to emulate his predecessor, Antonio Conte, in igniting a public feud with the former Porto, Chelsea, Inter Milan and Real Madrid boss.
"I think he will be able to win also in the future".
"I don't always take the right decisions", he said.
That is not going to happen at Old Trafford but Mourinho does think the 27-year-old's early season form is ominous so far under new Chelsea coach Maurizio Sarri. As many as eight first-team stars are doubtful or confirmed absentees for the match against Chelsea.
Manchester United have been fined €15,000 for the late arrival and subsequent behind-schedule kick-off of their Champions League game with Valencia, while Napoli must pay €34,000 for the setting off of fireworks against Liverpool.
"The problem is not the way of football, if I like it or not", Sarri added.
"He has won everywhere".
"I actually think it is a smart move from Jose to go to Stamford Bridge with a Jose Mourinho style of play, and come out of there with something".