United manager Louis van Gaal said that "everything was against" his side in the disappointing 0-0 draw in the FA Cup- but also praised "magnificent" Cambridge.
The Reds had 80% of possession in the second half at the Abbey Stadium but could not break down a resilient and stubborn defensive unit that deservedly forced an Old Trafford replay.
"I was angry at half-time because we made the same errors against Yeovil Town and also Queen's Park Rangers" explained the boss.
"We have played in the same style of play as the opposition and you do not have to do that.
"I know that also in these matches everything is against you- the crowd- that is nice, I think- but also the pitch and also the defensive organisation of the opponent and even the referee as well.
"In the second half we have played better, we have built the game up from behind and played no more long balls.
"Then we could have scored, we had many chances, but we did not do this so now we have to play this team again, this time at home.
"Cambridge are the weaker team-everybody knows that- and you have to solve that problem (of how to beat them) but you cannot always solve that problem and I have seen that a lot of times.
"But fortunately we are still in the FA Cup, we have to play at home and we have to beat them."
Cambridge were rank outsiders for Friday's tie and manager Richard Money was rightly delighted by his team's display against English football's most successful club.
Van Gaal lavished praise on the plucky opposition too.
"It's fantastic for them" he explained.
"I think a lot of players have dreamt of this and they fought with spirit until the end. Also, in the first half they have created one or two possibilities. You can lose these games and we haven't so this is good.
"It is not as easy as everyone was thinking.
"I'm very happy we're still in the FA Cup- we will have a better chance in the second game I think.
"Okay, we have to play another match but I don't think that's a bad thing because this season we don't play in European competition so it's good to have an extra game in February."
The replay at Old Trafford will be played on Tuesday 3rd February