Jose Mourinho bragged that Manchester United "totally controlled" Chelsea on Sunday, but the display against Anderlecht once again shone a light on their shortcomings on a night when victory came at a cost.
If the weekend win over the supposed Premier League champions in waiting was intended to set a benchmark for Mourinho's United, they wasted little time in lowering those expectations.
Thursday's performance - a profligate and nervy one punctuated by injuries for Zlatan Ibrahimovic and Marcos Rojo - was far from dominant and United survived a couple of scares before Sofiane Hanni pounced on a Youri Tielemans strike that had hit the crossbar to cancel out first-leg goalscorer Henrikh Mkhitaryan's opener.
It spoke to a vulnerability that has been apparent within United for most of the season, even amid a top-flight unbeaten run that now stretches to 22 matches.
The triumph over Mourinho's former employers should have imbued the hosts with the confidence to take the game to the Belgian side and wrap up a Europa League semi-final berth long before Marcus Rashford's coolly taken extra-time goal eventually secured that honour.
The Europa League may ultimately be a means to a more alluring end for a club of United's stature, but the silverware itself will go some way to restoring that confidence - which once, entirely justifiably, bordered on arrogance - at Old Trafford.
A return to the Champions League was Mourinho's most pressing objective when he took charge and that may yet come via a top-four finish, but the second-tier competition's bonus prize is perhaps a more likely route.
Yet it is one that could have been closed off to them here, as a wasteful second-half showing increased the nerves, with Ibrahimovic, Rashford and Paul Pogba all spurning excellent opportunities.
Ibrahimovic, who shot tamely at Ruben Martinez with one chance and skewed another embarrassingly wide, hobbled off at the end of normal time after a nasty looking fall, joining Rojo on the list of United's injury victims for the night.
The final is in his native Sweden and would be a fitting stage for he and United to close the season, but for a long time it seemed a lot further away than the 1,400 kilometres between Manchester and Stockholm.
While the veteran forward has so often been United's hero this season, it was a striker a little over half his age who stole the spotlight this time.
Rashford set up Mkhitaryan's opener and then pulled the release valve on the building tension inside Old Trafford, showing the composure that had eluded his more experienced team-mates to win it early in the second half of the additional 30 minutes.
1 - Marcus Rashford has scored his first goal in European competition since netting v Midtjylland on his Man Utd debut in Feb 2016. Timing.-- OptaJoe (@OptaJoe) April 20, 2017
There was still time for Frank Acheampong's last-gasp close-range header to give the home side a scare, one of many on a night that was nowhere near as straightforward as it should have been.
But nothing worth having ever comes easy, which - based on United's travails on two fronts in their pursuit of a return to Europe's top table - underlines just how much the Champions League means to the club.