The Dutchman's first appearance as United boss on home soil was greeted with enthusiasm by supporters, but even the renewed confidence cannot compensate for a patchy squad.
For all the talk of vast riches and links to a swath of stellar names, only Luke Shaw and Ander Herrera have committed to a team that is without Champions League soccer in the season ahead.
As a result, so many of the players written off as not being of sufficient standard under David Moyes are in position to play key roles as the Premier League kickoff edges nearer.
MORE: Coach Ted Lasso returns! | Porter challenges Guardiola | WAGs
But with a manager with the gravitas of Van Gaal in charge, none of that seems to matter too much.
Last season United fans descended into the type of doom only those who remember Ferguson's early years can relate to. Moyes never gained the respect or displayed the ability to overbear opposing teams, or even convince his own support, but with Van Gaal it is part of the package: a hugely experienced, slightly erratic, utterly commanding presence.
|MAN UNITED LATEST
Van Gaal's first Old Trafford appearance as United boss was greeted with predictable warmth by the club's fans, but the 90 minutes against Valencia served up plenty of reminders of the task at hand, friendly or not.
While the Dutchman's emergence from the tunnel before kickoff was greeted with enthusiasm, the match itself was standard preseason fare. Wayne Rooney missed a first-half penalty before Darren Fletcher's deflected shot bounced over Diego Alves. Tom Cleverley's dubious clearance allowed Rodrigo Moreno to lash into the net and equalize, but Marouane Fellaini, after his every touch was ironically and cruelly cheered by the home fans, bundled home a late winner to turn the irony to genuine joy.
As a result United secured an unbeaten preseason, having seen off the LA Galaxy, Roma, Inter, Real Madrid, Liverpool and now Valencia.
Some have even tipped the Red Devils for a title charge, but even this renewed confidence can surely not fill the gaping holes in the squad.
Deploying, once again, the 3-4-1-2 formation, United had Ashley Young and Phil Jones on the right side, as derided a duo as you could find in the club's recent past. We are still in friendly territory of course, where lineups and form are of no indication of future intent. But, in truth, Van Gaal doesn't have many other options.
Jones, Chris Smalling and Jonny Evans remain the three senior center backs, while on the flanks Young and Antonio Valencia remind those getting overexcited of the obvious limitations. In midfield the club is currently relying on Darren Fletcher to have recovered from serious illness and for Ander Herrera to take to English soccer immediately.
Van Gaal's supporters will point to the effectiveness of his Netherlands side at the World Cup as a case study for how a team with just one or two stars can still compete for honors. But there's a difference between a knockout competition and the long slog of a Premier League — or even top four — challenge.
Even on the basis of a preseason homecoming it's clear that this back line is too easy to get at, and not sufficiently organized to keep out midfield runners, particularly on the flanks. Those aren't problems that can be solved overnight, and given the strengthening of Chelsea, Arsenal, Manchester City and arguably Liverpool over the summer months, there need to be new additions to complement the good will and renewed optimism.
Van Gaal clearly knows the limitations: "The main thing is we won, despite playing our worst game," he said after the match.
The show-stopping signing, the one that United used to make in reaction to emerging threats, is surely still to come. If not, it could be a tough season by anybody's standards — especially Van Gaal's.