Ten Hag said: "It's very difficult (to keep changing the defence). Everyone who has a little bit of knowledge about football, they know it will affect your results and performances.
"The back four is always the foundation to get results - we didn't have that.
"We still have to win, we know that, so then others have to take responsibility, but when you oversee it then you know it has a negative impact."
On Maguire, he added: "You have to see it in that perspective. We were always happy with Harry Maguire, but he wants to play. He's a great leader, he's a very good defender, very comfortable on the ball.
"When I count all of those abilities, just now when we have problems on our defending line, he is even more important to lead that line, to make us play from the back.
"So we are very pleased he is there and we need him to get our results and achieve our targets."