Ten Hag: Main problem at Manchester United is 'lack of intensity'
United trailed 1-0 at halftime before Marcus Rashford, with a double, and Anthony Martial scored in the second half to inspire their comeback.
The win came four days after United were thrashed 6-3 by Manchester City in the Premier League.
"We have to carry on and every time learn the lessons and give the maximum, because only good for me is good enough - and at this moment, by far, we are not that good," Ten Hag told reporters.
"We have seen on Sunday and we have to do much better. I think the main problem is, and that is what we did in games before much better - intensity.
"We have to bring every game the intensity on the pitch. That was the big difference between City and us, so that is the demand to our squad, to all of our players, you have to take responsibility for that."
United, who are sixth in the league, play at Everton on Sunday.
