it says everything about the lunatic world of transfer deadline day that Arsenal paid out a straight £16m for Danny Welbeck because Arsene Wenger was up at 6am for an early flight and had more time than usual to have the necessary conversations.

His trusted chief scout, Steve Rowley, had watched Welbeck train for England at London Colney on the day that deal was done.

But did he see the video clip which asks searching questions about Welbeck's finishing and goes some distance to explaining his United strike rate of one goal almost every five games?

The film captures the moment, a little before 8.30pm under the Old Trafford floodlights on April 1, when Welbeck was presented by Wayne Rooney with a golden opportunity to put the ball beyond Bayern Munich's Manuel Neuer and give his side a lead in the Champions League last-16 first leg.

There was an electrifying atmosphere in the stadium that night but David Moyes needed Welbeck to shut it out and recall what he and the coaching staff had identified as the faintest element of predictability in Neuer: his tendency to leap up for the ball when faced with a one-on-one.

"Shoot low if you're sent through," Welbeck had been instructed.

Moyes held his breath in the split second that his player steadied himself. To his dismay, he saw Welbeck attempt to execute a chip, miscuing it so horribly that Neuer's comfortable stop was not strictly necessary.

The course of football history, and managerial careers, can rest on moments like that.

If – a very big if – United had progressed past the Germans, and Europe had provided professional salvation for Moyes, we would probably still be having the same conversation about the club's decision to release Welbeck.

Moyes valued him but a realisation that he was not the prodigious finisher United needed lay behind his decision to look to Paris Saint-Germain's Edinson Cavani.

Moyes personally scouted Cavani three times, only to go off the idea of bidding, concluding that he was not as good as Luis Suarez and over-priced at £65m.

Louis van Gaal has reached broadly the same conclusion about Welbeck. His assessment on Thursday that the 23-year-old is simply not United "standard" came with the added implication that the player was not willing enough to fit in with the manager's "philosophy".