United have been criticised heavily this term, but Robben has told the Mail that they are on course for a successful campaign.
Big things were expected of the club, but they have struggled to live up to these expectations, especially from an aesthetic point of view.
United may be winning games at an incredible rate, but they are doing so with little style, and Van Gaal has been criticised for not improving the club from David Moyes’ tenure last term.
However, United are still on course for a Premier League top-four finish - and the Champions League qualification that it guarantees - as well as looking to guarantee a place in an FA Cup semi-final when they take on Arsenal on Monday evening.
The next few weeks could ultimately decide if Van Gaal remains in the job next season, with three clubs also looking to overtake the Red Devils into the top four.
Although securing the FA Cup is not necessary, it would certainly not hurt the Dutch coach to win some silverware, and Robben believes that would aid him on his search for a successful campaign.
Robben, who played under Van Gaal at Bayern Munich, as well as for the Netherlands, has told the Mail that winning the FA Cup and finishing in the top four is all United need to do for van Gaal to have had a ‘great season’.
“I have a lot of confidence he will be a success,” the winger was quoted as saying. “He is a coach that needs time, to build his team up.
"When he qualifies this year for the Champions League – and he has a realistic chance of winning the FA Cup also – if that happens, he has had a great season. I know Van Gaal’s quality and I know he will get it right.”