Antonio Conte admitted his player selection was "very poor" after his 10-man Chelsea squad suffered a 4-1 setback at Watford on Monday night.
New signings Olivier Giroud and Emerson Palmieri were only named to the bench while Conte put out a formation with three defenders.
Tiemoue Bakayoko drew the crowd's ire even before he was sent off with a second booking on the half-hour, and though Eden Hazard scored an 82nd-minute equaliser, Watford went on to score three times before the final whistle.
But Conte thought the game was lost well before then, telling Sky Sports: "We performed very bad but maybe I made the mistakes with the starting XI today.
"My choice was very poor I think. It was very difficult to change something tonight."
Chelsea are now fourth in the Premier League table, 19 points behind leaders Manchester City, and only a point ahead of Tottenham for the last Champions League spot.
The defeat was Chelsea's second straight by three goals after last week's loss at home to Bournemouth and Conte admitted he knew this season would be a challenge.
"I tried to warn everyone about the difficulty of our path in the league and Champions League," he said.
But asked if he thought anything had changed in his position as Chelsea manager following the two most recent results, Conte said: "It is the same. I stay here, try to work and put all myself in the work.
"The pressure? Which pressure? What is the pressure? I work -- if this is enough it is, OK. Otherwise the club has to take another decision."
Asked by BBC radio what he thought of Bakayoko's abbreviated performance, Conte said: "Two yellow cards in a few minutes, for sure you have to pay attention to avoid this situation.
"It was a difficult moment for us and then to go down 10 men and play with 10 players it wasn't good."