Key lessons to be learned from Reds' deserved victory
1 Young striker Rashford is a natural leader
There is something liberating and, at the same time disconcerting, about seeing Manchester United's season largely hanging on the form of a teenager.
On the positive side, though, Marcus Rashford seems blissfully unburdened by the pressure on him.
The England striker has assumed a level of leadership in the absence of Zlatan Ibrahimovic that would consume most 19-year-olds and, just as he came to United's rescue in against Anderlecht with a finish of the highest class, so his free-kick here provided another timely reminder of his vast potential.
Just because Rashford is one of the quickest players in England, doesn't immediately make him a winger, and United seem to have realised that now.
With Ibrahimovic in the side Rashford was pushed out wide, but in his absence the teenager is looking back to his best.
Aside from the goal, as a centre forward, he was allowed to naturally run into channels and drag the centre-backs out of position, something that was often exploited by the likes of Jesse Lingard and Henrikh Mkhitaryan.
2 Killer instinct needs sharpening
When Paul Pogba slipped a lovely through-ball into the path of Mkhitaryan with only Sergio Álvarez, the Celta Vigo goalkeeper, to beat 34 minutes into the piece, Jose Mourinho must have known what was coming.
It is a scenario he has seen more times than he will care to remember this season. Mkhitaryan opened up his body but there was nothing that suggested he was confident he would score. The resulting shot had neither the power nor accuracy to beat Álvarez, who saved relatively comfortably.
For all Mourinho's bleating about injuries and fixture congestion, nothing has undermined United as much as a lack of ruthlessness in front of goal.
3 These are moderate opponents
Celta Vigo may have beaten Real Madrid and Barcelona this season but there is a reason why they are languishing in 11th place in La Liga, with 16 defeats in 34 matches.
They are a modest side at best, a team that the United of old would have brushed aside with the minimum of fuss, rather than making such heavy weather of it, as they did here.
Celta's purported high-intensity pressing failed to materialise and, for all the pre-match talk about Iago Aspas, the Celta forward looked very much here like the player who failed to make any impression at Liverpool.
Similarly, John Guidetti - honest but workmanlike - underlined why he never played in the Premier League for Manchester City.
4 Pogba's problems
The margins are thin in top level football and, while it would be easy to accuse Paul Pogba of having an underwhelming first season back at United, the reality is that his campaign would be looking very different if he had been playing with more forwards in front of him capable of finishing the defence-splitting passes that he produces.
He made a bursting run for which he should have been awarded a free-kick midway through the first half and then a second towards the end, which should have ended in a Mkhitaryan goal.
It was certainly one of his better games, but, given his strength, skill and passing ability, he should be dominating games like this.
Perhaps it is a little harsh to criticise him for his performance but, given his price-tag, he is always going to gather more harsh reviews than glowing ones.
Pogba is still in the shadow of that and, until he starts dictating games, it will always be used against him (© Daily Telegraph, London)