The Red Devils have secured the talented youngster to a long-term extension, while he has also gone out on loan.
Kovar has signed for Burton Albion on deadline day, which will give him a chance to gain regular first-team football.
The Czech shot stopper is now under contract until June 2023, which can be extended by another year.
"Kovar will come in and make life hard for Ben [Garratt] and provide some good competition at the club," said Burton boss Jimmy Floyd Hasselbaink in a statement.
"He will add some great competition, he is a young keeper and we felt like we needed another one in the door."
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