Mark Hughes was surprised Van Gaal dropped Rooney for the first time during his 18-month spell as United boss.
Louis van Gaal has hinted that he may resign before being sacked as Manchester United manager, as reported by The Independent.
Hiddink's first match in charge ended in a 2-2 draw at home to high-flying Watford after Oscar missed a second-half penalty that could have secured back-to-back wins.
Louis van Gaal has taken the brunt of the blame for United's slump, during which they have dropped to fifth in the Premier League, nine points adrift of leaders Leicester. For United, none of Matteo Darmian, Marcos Rojo or Jesse Lingard have recovered from their injuries, and so join long-term absentees Luke Shaw and Antonio Valencia on the sidelines.
"You can single anybody out when you are in these situations, but the only way to get through this is to work hard, stick together and keep believing it will turn for us, and it has to turn for us in the next game".
Van Gaal's future is looking increasingly uncertain after a run of six matches in all competitions without a victory, coupled with a series of uninspiring performances.
A day after British astronaut Tim Peake displayed a Stoke flag on the International Space Station, the central England team was in a different orbit to United in the first half.
Depay, a winger in the right back position, was unaware that Glen Johnson was primed to dart in and seize possession before crossing for Krkic, who took a touch then slotted the ball into the net in the 19th minute.
The 20-times English champions have always been associated with swashbuckling attacking football but, apart from a brief flurry after the break when Van Gaal brought captain Wayne Rooney off the bench having omitted him for "tactical reasons", they were woefully short.
Van Gaal admitted he has a big challenge in motivating his players to end the poor run of results.
And the mission facing United became even tougher seven minutes later.
United dominated possession following Rooney's introduction and were denied a route back into the game as Butland produced an excellent point-blank save to thwart Marouane Fellaini after the Belgian had met the England skipper's low delivery. His mood would have darkened further had Arnautovic scored another when through on goal moments later but luckily for United, the Austrian shot wide.
It was a hapless first-half performance, and Van Gaal questioned why his players "don't dare to play football". "That's a good signal", added Van Gaal.
In the closing minutes, Rooney this time set up Juan Mata but again Butland made the vital save.
United visit Hughes' Stoke in the Premier League this lunchtime - and are desperately in need of a win to lift them out of their current crisis. United is three points adrift of fourth-place Tottenham.
