He did not have a Gary Pallister alongside him, as the Neville brothers had in 1995. And his inexperience told when he kicked the ball straight to Wilfried Bony, allowing Swansea to take a quick free-kick in the run-up to Gylfi Sigurdsson's winning strike.
With Ashley Young's defensive struggles at left wing-back highlighted by the fact he was exposed for both goals, the need for reinforcements to make van Gaal's preferred 3-4-1-2 system work looked urgent.
Van Gaal's pursuit of Sporting Lisbon's Argentina defender Marcos Rojo and interest in Ajax wing-back Daley Blind - and failed attempt to sign Thomas Vermaelen - reveal his wish to add experience to his back line. Further upfield Arturo Vidal and Angel Di Maria remain targets, understandably so given United's lack of both pace and creativity.
There are echoes of last year when, as David Moyes recalled in a newspaper interview yesterday, United missed out on other targets.
"There was talk of [Cristiano] Ronaldo when I first arrived," Moyes said. "We were close to getting a couple of major names. I'm not getting in a blame game here but things just didn't materialise."
United can at least rely on Wayne Rooney, the new captain. He scored their equalising goal, hit the post with a free-kick and was seen running back to shout at his defenders after Sigurdsson's decisive strike.
Rooney said United's defending had let them down. "We know last season was a disaster [and] we were ready for the start of this season [but] conceded two sloppy goals and we have to learn from that," he said. "We have to be more demanding in what we are doing. We will learn, especially with the manager we have got."
What may take time is for van Gaal to restore United's old fear factor. Swansea had never won at Old Trafford until this year.