Chelsea stuttered to a 2-1 win over Newcastle United at Stamford Bridge on Saturday, with Jorginho enduring a particularly frustrating day.
The Italy international saw a lot of the ball and was generally accurate with his distribution, but he appeared to struggle consistently with the more complicated passes.
Chelsea fans seemed to get on his back on a few occasions and Sarri accepts the ex-Napoli player was "in trouble" at times, but he did not take him off as he felt there was no adequate replacement for him on the bench.
Fabregas would have been that option had the Spaniard not departed for Ligue 1 on Friday, and with the club reportedly stalling on deals for Nicolo Barella and Leandro Paredes, Sarri is eager for midfield options to arrive sooner rather than later.
"Jorginho was in trouble and on the bench there wasn't a player for that position," said Sarri. "I need an option for Jorginho.
"I have no idea [how soon a replacement will arrive].The club is worried, I don't know. The club knows very well my opinion.
"I need the player there, it depends on the club's decision, I think. I cannot do anything more."
Saturday's win was secured by goals from Pedro and Willian either side of a Ciaran Clark header.
It was by no means a convincing performance and Sarri was left in the belief Chelsea have a problem with their mentality.
"It's very difficult to understand. In the last five matches for us it really was very difficult to score," he said.
"[On Saturday] we scored after nine minutes, so the team thought it is very easy. We stopped to play and then we had problems.
"We were not able to react in the right way to the difficulty. [The Newcastle match] wasn't a difficulty. We scored after nine minutes, so we did not have to face difficulty.
"But in the last match, for the first time in Watford, we reacted very well to the 1-1, after the goal in the last minute of the first half.
"I think, apart from the result, we reacted really very well in the last match with Tottenham. [Against Newcastle] we had only to manage a positive situation. I think we need to improve our mentality."