He told Belgian TV channel Play Sports (h/t Football.London's Greg Johnson):
"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."
Hazard was taken off at Old Trafford for Pedro in the 73rd minute, with the score level at 1-1.
Two minutes after his departure Jesse Lingard fired United in front to win the contest, albeit Alvaro Morata had what should have been a late equaliser incorrectly disallowed for offside.
Per ESPN FC's Liam Twomey, Conte confirmed Hazard's withdrawal was a "tactical decision" and added:
The Belgian had been one of the most dangerous players on the pitch in the first half, as Squawka Football demonstrated:
Fatigue could be an issue for the Blues' top stars. Chelsea have scarcely slowed down since the gruelling festive period and have played 14 times already in 2018, with Hazard involved in 12 of the matches.
However, the Blues only have four fixtures in March, one of which the winger could be rested in—a home clash with Crystal Palace prior to the UEFA Champions League last-16 second leg with Barcelona—so it was an unusual decision to take him off with 20 minutes remaining in a key league match that was in the balance.
Per The Sun's Jake Heasman, Hazard is electric with the ball at his feet:
Football writer Jordan Clarke noted the effect his skills have on opponents and opposition fans:
He has been in good form of late, too, having contributed six goals and two assists in the seven matches prior to facing United, against whom he set up Willian's opener.
While the winger's showing in the second half was not as strong as the first amid an excellent performance from United's Scott McTominay, Hazard has the talent to change games in an instant, so taking him off was perhaps an error on Conte's part.