United completed the signing of Matic for £40m at the end of last month, reuniting the Serbian with his old boss Jose Mourinho.
Chelsea’s willingness to sell the player drew criticism from numerous figures within the sport, with Paul Scholes most recently questioning the decision to let him go.
And speaking in a recent interview with Sky Sports, the Italian boss described Matic’s departure as “a great loss” for the club but one that he had to "accept".
"Matic knows very well what I think about him," he said. "The importance for me about this player, who is a really good player, a top player, very important for our team, but sometimes you must accept this crazy transfer market.
"And sometimes you must accept different decisions. But he is a great loss for us."
Conte also warned that Chelsea must bring in more players to have any chance of successfully defending their Premier League title.
The champions have so far signed the likes of Monaco midfielder Tiemoue Bakayoko, Real Madrid striker Alvaro Morata and Roma defender Antonio Rudiger, but Conte has insisted Chelsea still to strengthen before the transfer window closes on August 31.
"Yes, for sure," the Italian said when asked if it will be hard to retain the title this season without making more signings.
"This league is not easy. Six teams are very strong and you must be prepared. I hope to be able to improve our squad. The transfer market is not finished. We want to be competitive and we want to fight for the title again. The club knows my priorities.
"It won't be easy. It's a great challenge for us to try and retain the title, but we are working hard."
Conte added that he was optimistic Morata, who Chelsea signed for a club record £70m, has a bright future ahead of him at Stamford Bridge.
"Alvaro is a really good player, he's still young despite having a lot of experience," he said.
"He needs to play regularly, he's a player I trust a lot. I think he has good prospects for Chelsea - for now and the future.
"Will he start this weekend? He's working very well and starting to understand or idea of football."
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