Conceding an injury-time equaliser to AC Milan last week prompted a heated discussion at Manchester United.
It wasn't a row but strong words were exchanged and manager Ole Gunnar Solskjaer was confident that his message had got through to his players.
There could be no repeat of what happened at Old Trafford. No more switching off in the dying seconds of a game. No more set-piece sloppiness.
The talking-to appears to have worked, judging by the almost impeccable defensive displays in the two 1-0 victories that followed, against West Ham, in the Premier League, and Milan, in the Europa League second leg at San Siro.
The only shame, perhaps, is that Solskjaer's message wasn't taken on board earlier. Just two months ago, United were in contention to win the league.
However, their title hopes were being hindered, and would eventually be undone, by sloppy defending and careless goalkeeping.
The 3-3 draw with Everton at Old Trafford, when United blew a two-goal lead in the closing stages, was the perfect case in point: Solskjaer's side were lethal going forward but porous at the back.
At that stage of the season, they had conceded more than twice as many goals than table-toppers Manchester City (30 to 14) and it ultimately cost United a real crack at the title.
Still, since the Everton setback, United have shown undoubted improvements in their defensive work. They have let in just two goals in their last six league games, and just three in their last 11 outings in all competitions.
Solskjaer insisted throughout the season that his confidence in his back four always remained "sky high".
However, it was no secret that United were evaluating several centre-backs with a view to strengthening the defence during the summer transfer window.
Sevilla's Joules Kounde, Real Madrid's Raphael Varane and Braga's David Carmo are just three of the players that have been monitored closely.
Getty/GoalHowever, the situation has now changed, and United's display in Milan on Thursday night underlined why.
The much-maligned Victor Lindelof put in one of his best performances in a United shirt, making five important clearances and interceptions, Luke Shaw continued the fine form that has earned him an England recall, while Harry Maguire was, once again, solid as a rock.
It seems the problems that plagued the defence earlier in the campaign have, for now at least, been ironed out.
“That is down to a lot of good work on the training ground,” Solskjaer told reporters. “Of course, we’ve been drilling the back four but it’s a team effort and the coaches have really, really worked on details that we’re improving on every game.”
Nonetheless, Lindelof, who was man of the match against Milan, has been particularly impressive of late, looking far more secure alongside Maguire at the heart of the defence.
“Victor and Harry, they've got a good understanding with each other and have really built on last season,” Solskjaer argued.
“Then again, we have other centre-backs here who come on and play well when they have the chance.”
The challenge now, of course, is for United's central defenders to maintain this level of performance because the problem with the back-line, like the team in general, has been a lack of consistency.
Getty/GoalWhile United have been keeping more clean sheets during the past month, they remain susceptible to mistakes, especially when it comes to defending set-pieces or shackling players with exceptional pace.
The inclusion of Eric Bailly can make up for the lack of speed in the centre of defence but the difficulty with the Ivorian is keeping him fit and happy.
However, with the back four now having seemingly cut out the costly errors and lapses in concentration, and Solskjaer downplaying any speculation over the club looking at a centre-half, the focus for the upcoming transfer window has now turned to the misfiring forward line.
Marcus Rashford has scored once in six games, Anthony Martial has netted just four times in the league all season, while Mason Greenwood and Daniel James have now gone 15 and seven games without a goal, respectively.
Even United's talisman, Bruno Fernandes, has contributed one goal in his last seven appearances.
The free-flowing, fluid attack that propelled United to the top of the table have lost that final-third precision that so often makes the difference at this level.
Given Edinson Cavani is likely to leave at the end of the season, Solskjaer has a big decision to make over whether to go all out to sign a natural No.9 this summer.
Erling Haaland is obviously the dream. After all, who wouldn’t want the prolific Borussia Dortmund striker? However, financial constraints caused by the coronavirus pandemic would make a deal for the most in-demand centre-forward in world football right now very difficult to pull off.
United, then, have some thinking to do. But if the performances of the last few weeks continues through to the end of the season, United may well end up making a striker rather than a centre-back their priority in the next transfer window.