And, most emphatically, that it is high time to dispel the myth about the strength in depth of United's squad.
Alex Ferguson used to have a deep pool of players into which he could plunge in order to rotate his squad and keep everyone fresh. But the days of being able to call the likes of Teddy Sheringham and Ole Gunnar Solskjaer off the bench are long gone.
United simply do not have a strong squad any more. You only need to take a cursory glance at their first-team list to see there are just 13 that you could justifiably call top class - and that includes Ryan Giggs and Paul Scholes, who are far from the players they used to be.
The rest are a sorry collection of has-beens (Gary Neville, Wes Brown), perma-crocks (Michael Owen, Owen Hargreaves), players who really should be doing better (Park ji-Sung, Michael Carrick, John O'Shea, Jonny Evans), pointless foreign imports (Tomasz Kuszczak, Anderson), youngsters (Chris Smalling, Gabriel Obertan, Fabio, Federico Macheda) and Bebe, who fits into at least three of the above categories.
Those who were in the side that were out-maneuvered, out-thought and out-fought by West Ham should count themselves extremely fortunate should they ever pull on a United shirt again.
You can see Ferguson's pre-match thinking. West Ham are poor. Very poor. Despite victory at the weekend they still prop up the rest of the league and have showed little or no evidence they have what it takes to stave off relegation from the top flight this season.
Factor in the six changes Avram Grant made to his own side (compared to United's 10), including the resting of his one genuinely decent player Scott Parker, and it was easy to see that it would take quite something for United's second string, no matter how poor they are, to be troubled by the Hammers.
But that's what happened as United caught West Ham on a rare good night, and the Reds' purported 'strength in depth' was horribly exposed as nothing more than a sham. United may be at the diametrically opposite end of the Premier League table to West Ham, but they are only on top at the moment because teams around them are struggling to find any kind of consistency.
As they have found out to their cost this season (Liverpool and Blackburn games aside), when your star player is not performing, another needs to step up to the plate and deliver the goods. When your squad is incapable of volunteering that player, problems arise.
With Wayne Rooney's problems well documented, United have been forced to look to Dimitar Berbatov (who has put in two outstanding performances all season, and little else), Javier Hernandez (eager, but raw), Owen (far, far too injury-prone) and Macheda (just no). Hardly outstanding alternatives for Ferguson to turn to. And that's not to mention defensive cover - or the lack of it - and the threadbare midfield.
Genuine strength in depth is a pre-requisite of winning trophies over the course of a long, hard season - to cover for injuries in the league and to provide a decent second string in cup competitions like last night.
United simply do not appear to have that. And as the season goes on, Ferguson's refusal (or inability, depending on who you believe) to reinforce that small band of 13 top class players with more of a similar ilk last summer will increasingly come back to haunt him.