Manchester United midfielder Marouane Fellaini says the Red Devils have to be fully focused on the job if they are to lift the FA Cup at the end of the season.
With big teams crashing out early in the competition, United remaining the only top-four team in the competition and the 27-year-old believes van Gaal's side is a strong contender to lift the trophy.
"We created a lot of chances and we could have scored more goals," the Belgian told MUTV.
"But 3-0 is good. It was a great chance for them [early on when Tom Elliott hit a post] but the most important thing, in the end, is we won the game and we are through to the next round."
The former Everton man was deployed in a more offensive role against Cambridge United and was one of the best players on the pitch.
"It was okay [playing in attack]. The manager decided for me to play there. It was good for me. I played and we won so it's good for the confidence as well.
"In England, the FA Cup is a very big competition so it's good to be there [in the fifth round].
"We have to stay focused for the next round and work hard together to get through again. It's difficult to play against these teams.
"It's the FA Cup so anyone can win a game. That's why you have to stay focused and be ready.
"When you don't concede a goal and you win, it's good for the confidence - for the players, for the club, for the supporters - so we have to keep going."
