Louis van Gaal declared himself a "happy coach" after United's 3-0 over Ipswich on Wednesday as a strong Reds side progressed into round four.
"The result was great, we don't have injuries, I brought in players, I rotated players and Phil Jones has played some minutes so I am a happy coach." said the Dutchman.
On fielding a near full-strength side:
"Last year we were out in the first round against Milton Keynes away and this was not good, at that time there were a lot of injuries and I played with my second team.
"We went out and the fans were not so pleased, I thought that this year I should do it another way so played with mostly my first team.
"We play also at home so we have to make it enjoyable for the fans as well, our own fans.
"We have succeeded in doing that and that's a major point for me, we have no injuries, we have won and we are into the next round."
"The first goal I liked the most because it is a fantastic pass from Daley Blind and the way Wayne Rooney finished it was great because it was not so easy.
"We know that Pereira has the quality to do that with the free-kick so that is also good, of course then there was Martial's goal, in the last 15 minutes the gaps were bigger so it was easy for him."
On Boro at home in round four:
"It is another top club in the Championship, I do not know much about this opponent, the scout shall analyse them like with Ipswich.
"It is one of the top clubs so it is not easy but I am pleased because we are at home and I am happy because this gives us a good chance of getting into the next round and we do not have to travel."
On Anthony Martial, LVG added:
"It is not so difficult because he is a player who is very modest, he knows that he can score and he can also do this because of the other players in the team.
"We made it for him two times very easy because we won the game and the gaps were existing.
"With his speed and composure, he can score always.
"He did it against Liverpool, against Southampton two times and now again.
"He is happy and I am happy but we have to keep his feet on the ground."