Van Gaal seems unimpressed by what he's seen from the midfielder in Brazil where he's had the opportunity to prove he can be important for United next season.
In some respects, Fellaini's form for his country is far from the abject showings Man United fans were treated to throughout his debut campaign at Old Trafford.
|Team||Pos||Aerial Duels Won||Apps||Mins|
|Daniel van Buyten||Belgium||DF||19||4||390|
For starters, Opta stats show that Fellaini has won the third-highest amount of aerial duels in Brazil, demonstrating his considerable threat in the air.
His aerial ability was also crucial when he scored his side's first goal of the tournament during the 2-1 comeback win against Algeria.
Belgium team-mate Daniel van Buyten tops the list, with Greece's Georgios Samaras in second. Fellaini, however, is just two behind Van Buyten and may well overtake him by the end of the tournament.
|Team||Pos||Dribble Success Rate (%)||Dribbles Won||Apps||Mins|
|Daniel van Buyten||Belgium||DF||100.00||1||4||390|
On the ball, meanwhile, the 26-year-old has completed all five of the dribbles he has attempted, making him the most accurate Belgian when it comes to taking on his man.
Chelea's Eden Hazard trumps him in terms of amount won, of course, but the Man United midfielder's flair in Brazil has been both impressive and surprising in equal measure.
|Team||Pos||Tackles Won||Interceptions Won||Pass Accuracy (%)||Successful Final-Third Passes||Apps||Mins|
|Kevin De Bruyne||Belgium||MF||8||6||83.22||52||3||300|
And Fellaini's contribution doesn't stop there, with the former Everton man also proving adept in a defensive capacity, as well as completing the third-highest amount of final-third passes in the Belgium squad. His overall passing accuracy (77.69%) is the only real area that lets him down.
So while the Fellaini we've become used to at Manchester United flounders in big games, the Fellaini of the World Cup has been a key presence in Marc Wilmots' Belgium side. And with the Belgians into the final eight, there is nothing to suggest the 6ft 4 midfielder won't be leaving Brazil with a medal of some kind.
That's not to say these performances mean Van Gaal should consider keeping Fellaini at Old Trafford, but it's interesting to see what Fellaini can produce under different circumstances, a side to the Belgian that Man United fans are yet to really discover.