As most of the debate around Sir Alex Ferguson's team selection for last week's controversial Champions League defeat by Real Madrid centred around Wayne Rooney's omission, what a significant day it was for Welbeck was overlooked.
United's goalscorer in the first leg, and preferred ahead of England's talisman in the second, Welbeck has made giant strides over the past month, proving that not all his best performances have been reserved for the international stage.
Yet Robson accepts the 22-year-old still has work to do.
After all, that header in the Bernabeu remains one of only two goals for Welbeck this season.
That is fewer than Rafael, Jonny Evans and Patrice Evra, let alone top-scorer Robin van Persie, Javier Hernandez and Rooney, the latter two heading for the 20-goal barrier their Dutch team-mate has long since crashed through.
And that is the area Robson believes Welbeck must improve if present progress is to continue.
Speaking at the launch of the 'Legends are Back' game between Manchester United and Real Madrid, which will take place at Old Trafford on June 2, Robson said: "A few of the younger lads have progressed really well this season.
"But it was a measure of how well Danny has come on that the boss put him in the team ahead of Wayne Rooney last week.
"That was such a big decision but Danny has all the attributes you need, apart from being a natural finisher.
"The good thing about it is that is an area you can work on and improve. And I know Danny will do that because he is a keen lad with such a great mentality towards the game."
As England's top scorer in 2012 and one of five players nominated for Three Lions' player of the year, Welbeck, to an extent, left Rooney in the shade last year.
Not in terms of personality, though.
As the foremost player of his generation, Rooney has been the centre of attention, for good and bad, for over a decade now.
So Robson was not in the least bit surprised that there should be so much talk about the 27-year-old being left out by Ferguson last week, nor that the extension of that chatter should focus on whether Rooney had a future at Old Trafford.
Yet Robson claimed Ferguson had previous form for the kind of marking job the Scot asked Welbeck to do on Xabi Alonso last week, for he got Brian McClair to carry out a very similar task on Ronald Koeman in the 1991 Cup Winners' Cup triumph over Barcelona in Rotterdam.
"The boss had not spoken about it at all until the team talk before the game, when he told Brian what he wanted," said Robson.
"He was our centre-forward, but he had to do it.
"We went on to win the game and the boss was proved correct.
"It was the same with Danny. It was a tactical decision, that is all. At big clubs they happen all the time and players have to abide by them.
"I realise the suggestion afterwards is that the boss has run out of patience with Wayne but I don't think that is the case at all.
"Purely and simply, he was trying to find the best way of getting into the next round and, but for one decision by the referee, I am sure it would have worked."