The defenders signed contracts on Tuesday from Bayern Munich making United their third team together, and they could both feature in the squad's season opener on Friday against Fulham at Old Trafford.
Erik ten Hag will have newcomers Matthijs de Ligt and Noussair Mazraoui available for Friday's season opener just days after they signed from Bayern Munich, but the manager lamented that his team is not quite ready for the new Premier League campaign.
United kick off their season against Fulham at Old Trafford but have had little time to integrate the new players, Ten Hag said.
"It's true, it's not the pre-season where in five to six weeks you work on a team, it's very complicated," the Dutchman said at a press conference on Thursday.
"The USA tour squad, and then we added the players (who had been at) Euros and Copa America and now new signings, and we have to make a team from it.
"That team is not ready, but the league starts and more managers have this problem. Still, we have some room, have some principles and we have to make a start. We can't hide, we have to deal with it."
Harry Maguire will feature in Friday's squad after the defender missed England's Euro 2024 campaign due to his recovery from injury.
But left back Luke Shaw will not be available. Shaw played in England's final three games at Euro 2024 after battling a troublesome hamstring injury that resulted in him missing most of last season.
"He will return in the short term, it doesn't take long," Ten Hag said. "We are looking forward, of course, for Luke Shaw. A very important player for our team so we want to get him back as soon as possible but we can't force this process."
Ten Hag said Mazraoui, Lisandro Martinez and Diogo Dalot can all fill in at left back.
While there was plenty of speculation about Ten Hag's job last season as United finished eighth in the Premier League, the 54-year-old signed a new contract to stay at the club until 2026 after they upset Manchester City to win the FA Cup.
Ten Hag has high hopes for the team this season.
"We know our targets, we know our direction," he said. "Now we have to integrate new players where we think they can improve the team levels and to take it from there.
"(Our expectations) are always very high, we want to go for trophies."
United's new centre-back Matthijs de Ligt said his long playing partnership with Noussair Mazraoui will be a big boost to United's back line, an area that was decimated last season by injuries.
The defenders signed contracts on Tuesday from Bayern Munich making United their third team together, and they could both feature in the squad's season opener on Friday against Fulham at Old Trafford.
"What can I tell you about Nous? He is an amazing guy, an amazing player," De Ligt said in an interview with the team's in-house media.
"I've known him already for a long time, I think around 10 years now. There's a reason we always come together, like before in Ajax, then at Bayern Munich, now at Manchester United," the 25-year-old Dutch defender added.
"I think it is a special relationship and I'm really happy and glad that he's also going to be here, and I think we can help each other a lot."
De Ligt, who signed a deal until 2029, and Mazraoui, whose contract runs until 2028, have played more than 100 games together at Bayern and Ajax.
They also know Erik ten Hag well, having both played for the United boss when he was Ajax manager.
"He has played a big part (in my development), to be fair. He was the first trainer who made me captain, I was 18 years old and he just gave me so much confidence," De Ligt said of Ten Hag, who made him the youngest captain in Ajax's history.
"He told me right from the start: 'You are an example for the team, and I want you to be captain.' Just the confidence he gave me at that time, at that age, was really special."
United have largely rebuilt their back line from last season, which is part of what drew De Ligt to the team, he said.
"I actually really like the project," he said. "It's always nice to go somewhere and to feel that you're part of a new project, to feel that you're part of something new."
"Hopefully myself, and the other players that are coming this summer, can give a great piece to the next history of Manchester United and to get the club back to where it belongs: on top."
WOW Moments From Paris Olympics!
Olympics breakdancer Raygun opens up about online hate
Grand Chess Tour: Praggnanandhaa's bad run continues
We should have won the gold medal in Paris: Sreejesh