Hazard provided the assist for Willian’s opener at Old Trafford on Sunday, but the Belgian ace was taken off in the 73rd minute and the Blues eventually fell to a 2-1 defeat, with Jesse Lingard scoring the winner for United within two minutes of Hazard’s exit.
Courtois believes losing his international team-mate was the turning point of the game, and admitted Blues boss Conte ‘must explain’ why he took off their chief attacking threat in such a vital stage of a vital game.
Speaking to Belgian TV channel Play Sports, Courtois said: “I have no explanation for the sub of Hazard.
“I had not expected him to take him off but it is a choice of the manager. He must explain. I can’t look into his head.
“Players like Eden should have 90 minutes on the pitch. He can always bring something extra offensive.”
The defeat to United was the second game in a row where Chelsea’s defensive frailties were questioned.
They were 15 minutes away from a brilliant win over Barcelona in the Champions League before conceding a late Lionel Messi equaliser in a 1-1 draw at Stamford Bridge.
And Courtois believes that with Hazard still on the pitch, Chelsea would have had a better chance to claim at least a share of the points against United.
He added: “After our goal, we conceded a counter-attacking goal just like last Tuesday but in the second half we had less of the ball, but even then we should never have lost this match.
“If you do not do the small things well in top matches, you lose, which is what happened today.”
The goalkeeper’s comments are unlikely to go down well with manager Conte, whose future at Chelsea is under the spotlight amid reports he will be replaced in the summer.
But they also put more focus on the uncertain futures of Courtois and Hazard, who have both been linked with moves away from Stamford Bridge to Real Madrid.
Both players are said to be in talks with the club over new long-term deals.
Courtois has 18 months left on his current contract but has courted interest from Real, having admitted he is keen to return to the Spanish capital when his children and their mother still live.
Hazard’s Chelsea contract is due to expire in 2020, but the Blues are frantically trying to sign the 27-year-old to fresh terms, including a new bumper wage packet, amid strong interest from the Spanish giants.