We haven't be able to do it under Van Gaal so far, so what makes you think it'd be down to him in the future? I'm yet to see us play our way out of dangerous situations/pressure with tidy possession game. All we do when under pressure is hoof the ball up to absolutely no one , giving the ball away in the most moronic manner possible while the players become nervous wrecks.
Most of the players are way too limited with the ball, even the ones signed by Van Gaal (with some exceptions, but even Blind makes things hard for himself sometimes), so that'd explain our inability to string two passes together when pressed. Problem is, he's been here for over 18 months now and has done feck all to address the issue that's been a problem even before his arrival. Don't confuse clueless attacking play and lack of creativity against defensive teams with actual possession football.