United's midfield linchpin Casemiro (30) is suspended for the next three matches after being sent off in Saturday's 2-1 win over Crystal Palace, while midfielder Scott McTominay (26) and forwards Anthony Martial (27) and Antony (22) will miss the game with injuries.
Creative midfielders Christian Eriksen (30) and Donny van de Beek (25) are out with long-term injuries.
"We have a squad, we have many good players available in that squad, who are not always in the starting 11. So others get the chance," Ten Hag told a news conference on Tuesday.
"After the game, I can't say 'Casemiro is not there, Anthony Martial is not there'. No, we have to win. This squad, all players are Man United capable, so they have to perform tomorrow and we have to win the games, no matter who is coming on the pitch."
The manager also confirmed United had no plans to appeal the red card against Casemiro, saying the club did not believe it would be successful.
Wednesday's match was supposed to take place last September but was postponed after the death of Queen Elizabeth II.
Ten Hag's side will play Leeds again on Sunday, aiming to continue their remarkable run of form which has lifted them to third place in the Premier League table, eight behind leaders Arsenal.
Leeds sacked American coach Jesse Marsch on Monday, a day after a 1-0 loss at Nottingham Forest extended their winless run in the league to seven matches and left them 17th in the standings on 20 points, only above the relegation zone on goal difference.
Leeds' under-21 coach Michael Skubala will take charge of the game at Old Trafford alongside Marsch's former assistants Paco Gallardo and Chris Armas.
Ten Hag said he was sad to learn of Marsch's dismissal, adding that a change in coach mid-season does not usually lead to better results.
He also refused to be drawn on the charges against United's rivals Manchester City, who the Premier League accused on Monday of more than 100 alleged breaches of finance rules.
"I am not here for regulations. I am a football manager. I stick to that," he said.
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