Cape Town - Manchester United manager Louis van Gaal said on Thursday that cup upsets in his native Netherlands means he will take nothing for granted when his side faces Cambridge United in the FA Cup.
United, who last won the FA Cup in 2004, face the lowest ranked side left in the competition when they go to Cambridge, who are mid-table in the fourth tier of English football, on Friday night.
But van Gaal believes the physical presence of the home side, which only regained its place back in the Football League last season, means they will still pose a threat in the fourth-round tie.
He said: "It is always tough to play against, in the mind, weaker teams because in the players' mind it's a weaker team.
"For example, on Wednesday PSV Eindhoven - the number one in the (Dutch) league - lost against the number three of the second division (Roda JC) and it shall happen also in the FA Cup.
"There are always surprises and I hope we are not the surprise. When you see Cambridge and analyse them, they play very direct with long balls.
"They have five or six players above one metre, 90 (six feet, two), so for us it is difficult to defend. That's why you have to prepare yourself very well. It is not so easy to beat Cambridge United."
Van Gaal confirmed that striker Robin van Persie and defender Luke Shaw are fit to return after missing United's 2-0 win at Queens Park Rangers last weekend.
Defenders Chris Smalling and Jonny Evans are out, along with wing-back Ashley Young, but van Gaal looks certain to select a strong side.
United suffered the embarrassment of going out of the Capital One Cup to League One side Milton Keynes Dons earlier this season and van Gaal won't want a repeat in a competition which provides United with their last realistic chance of silverware this season and which van Gaal recognises as a major honour in the English game.
He added: "It is different more in the atmosphere I think. Here it is very important for the fans and people and players - that's the difference.
"Okay in Germany it is fantastic if you win the cup but not like here. Also the attendances are much higher here than in Germany or Spain
"Of course when you play Barcelona or Athletic Madrid there is always a full crowd but there are not many matches in Germany and Spain like that.
"In the Netherlands the cup is not so important but in the last years it became much more important. In the Netherlands Ajax, PSV and Feyernoord are out of the Cup - that's remarkable. It will be a long time before that happens again."
Darren Fletcher may also be involved for United at the Abbey Stadium but van Gaal was able to offer no guarantees the long-serving midfielder, 30, will still be at Old Trafford at the end of January with West Ham and West Bromwich Albion chasing the Scotland international.
"I'm not sure. It is the transfer month," added van Gaal.