He's a fine coach, whose Napoli team is easy on the eye.
My gripe was more that whenever there has been a key game in recent memory involving Napoli, they have fluffed their lines (Bilbao, key games against Juve, Dnipro, Roma etc.).
And that is not only Sarri's failing (Benitez was in charge against Bilbao, for example) but also the club's. ADL sets the tone when he privileges one tournament over the other, which I think has harmed Napoli more that it has helped them.
I have reservations about Sarri the psychologist, motivator, or trascinatore. I am not suggesting that a tub-thumper is what is necessarily required, but Napoli look really unprepared sometimes. The capitulation to Leipzig at the San Paolo was particularly disappointing, albeit predictable.
There was no excuse for Napoli to fold like they did against Roma either. I thought that was pretty bizarre especially when you consider there had been no European exertion a few days earlier. Had they won, they would have gone 7 points ahead of Juve, and Juve would have to play their game in hand with a lot more pressure.
And speaking of Roma, when they won the Scudetto last in 2001, Capello managed all aspects of the team well. You need that type of coach sometimes to break the mould at a club, especially a club like Napoli or Roma, where the organizational structure isn't as sound as Milan or Juve. I think back, for example, to that 2-2 against Juventus in the 2000/01 season, when Nakata scored that bullet from long-range. Roma were down 2-0 at one point, and it looked pretty grim.
Sure, it helps when you have players like Batistuta, Totti, Montella etc. but Napoli also have a lot of quality, and some players are playing beyond themselves--I'd be curious to see how Ghoulam and Callejon fare outside of this Napoli, for example.
I am not suggesting Capello is an awesome coach, or that Sarri isn't; more, I have doubts about whether Sarri can finish the job.
If you're asking whether I would like Sarri at Milan, then I would have to say no.