The Spaniard returned to the Blues starting line-up last night for their 1-0 Europa League win against Greece side PAOK after being left out again at the weekend.
The former Real Madrid striker was left frustrated though after missing several decent chances and was taken off with 10 minutes to go.
Morata shrugged off an attempted embrace from his manager and trudged towards the away bench, after another wasteful night in front of goal.
In the Premier League, Sarri has preferred to play Olivier Giroud in recent matches and the French World Cup winner has impressed.
And former Napoli boss Sarri believes that Morata is currently suffering a crisis of confidence.
The Italian tactician told reporters after the game with PAOK: “Alvaro has to gain confidence with one, two, three goals. I am not able to give him confidence.
“In this match he has had three, four opportunities. He was unlucky.
Despite failing to find the back of the net, the 59-year-old was pleased with his alert positioning.
”I have to say also, for maybe the first time in this season Alvaro was ready in the box. He was on the ball and was active,” he added.
“So I am really very happy with the three points, very happy with the performance I think, but I am not very happy with the result. When it is time to kill the match we have to kill the match.”
Morata – who could cost Chelsea up to £70m if all the add-ons in his deal are met – failed to fully impress last season.