Louis van Gaal claims he's 'proud' after Manchester United's derby win
Rashford was the star of the show with his 16th-minute winner proving the difference between the two sides.
The win moves United to within touching distance of their rivals and one point off the Champions League qualification places.
And Van Gaal has admitted it was a good day at the office for the Red Devils, and he's 'proud' of the performance of his players - especially after the quick turnaround from the Europa League defeat to Liverpool in midweek.
"We played a very good first-half with a goal and also had more chances and we didn't receive a lot of chances against us," he said.
"In the second-half we had to start again, we started well but after that we had to fight till the end because we were tired from playing on Thursday.
"They played on Tuesday so that is two days more rest which is important - I am a very proud manager today.
Marcus Rashford - 5 things you need to know
Invalid email
We use your sign-up to provide content in ways you've consented to and to improve our understanding of you. This may include adverts from us and 3rd parties based on our understanding. You can unsubscribe at any time. Read our Privacy Policy
"This victory was necessary, the gap was four points and now is one point, plus we are equal with West Ham which is important, what is possible? I cannot say.
"We do not have Thursday matches now and that is a positive thing.
"Rashford is very quick and Demichelis looked like the years are catching up with him. He was a very good defender, he was my centre-back in Bayern but that is the life of football."