United moved to the top of the Premier League after seeing off stubborn Sunderland with strikes from Memphis, Wayne Rooney and man of the match Juan Mata.
In the absence of a recognised left-back, Van Gaal brought Antonio Valencia in at right-back and moved Matteo Darmian across to the left, and LVGs' attack minded team started the match on the front foot.
The hosts good start was almost rewarded with an early goal in the sixth minute when Darmian's cross narrowly evaded Anthony Martial, and then Memphis squandered a half-chance from Michael Carrick's reverse ball.
Sunderland responded well as the Black Cats- in their bright green away strip- began to assert themselves on the match but, a John O'Shea header aside, chances were at a premium for the visitors.
Mata fired a free-kick into the wall whilst Jermaine Lens almost gave Sunderland a shock lead when played through at the Stretford End, but David de Gea saved well with his feet shortly before half-time.
United had been frustrated for long periods and looked set to go in at the break goalless, but launched one last attack and took the lead in the dying seconds of the half.
Daley Blind's superb pin-point pass picked out Mata who in turn cushioned the ball down for Memphis to tap home his first Premier League goal in added time.
Having secured the vital breakthrough moments before the interval, United doubled the lead minutes after it when the excellent Anthony Martial received the ball from Mata, outfoxed Younes Kaboul and then lashed across goal where the ball struck the onrushing Wayne Rooney and diverted into the net.
Lens went close with a free-kick and de Gea saved well from Patrick van Aanholt in a brief flurry from the visitors, whilst Memphis fired straight at the keeper after good work from Martial.
Mata was kept out by a super save from Costel Pantilimon but the Spaniard was not to be denied and got his deserved goal in the final minute when he fired into the roof of the net from Ashley Young's cross to seal a fine day at the office for the new league leaders.
United Faithful Man of the Match: Juan Mata
Overall team performance: 7/10