Last term Matic made 35 league appearances as Chelsea romped to the title.
'Matic knows very well what I think about him, ' Conte told Sky Sports. He described losing the Serbian as a "great loss" and a decision he must "accept".
Matic's former team-mate and Chelsea captain Gary Cahill also appeared to question the decision to sell the player.
'But sometimes I think you must accept this insane transfer market.
"I think he's very similar in a way to Michael Carrick in a controlling midfielder, but what he brings what Michael doesn't bring is a little bit of aggression which as I say he gets to the ball, he tackles, he allows other people to play".
Conte expressed unhappiness over the deal that took Matic to Old Trafford in an interview earlier this week, saying the Serbia international's departure was a "great loss".
Asked if Chelsea need more signings in order to successfully defend their Premier League title, Conte replied: "Yes, for sure".
Chelsea have signed Tiemoue Bakayoko as a replacement, although the France global will miss the start of the season through injury.
After an impressive pre-season, United will now look to prepare for their Premier League opener against West Ham on Sunday.
"It won't be easy. It's a great challenge for us to try and retain the title, but we are working hard".
The silver lining for Conte this transfer window appears to be beating Manchester United to the signing of Morata.
Chelsea's marquee signing this summer was the club-record arrival of Morata from Real Madrid for an initial fee of £58 million.
Asked if he would start against Burnley on Saturday, Conte said: "He's working very well and starting to understand our idea of football".