Sheer bloody-mindedness, unblinking concentration and strict organisation - without all that, they will take you apart at the Bernabeu piece by agonising piece. In this stadium, against these Real Madrid players, destruction is only a heartbeat away so getting out with their Champions League lives intact represented some achievement for Manchester United.
In fact, by the end it was the United players who surrounded the German referee Felix Brych to protest about him blowing the final whistle as they prepared to take a corner. Yes, there were times when they were on the rack but the storm that Madrid whipped up in the first half especially had subsided by the end and United might even have stolen it on one of their few counter-attacks.
Robin van Persie had a shot kicked off the line by Xabi Alonso which, had it gone in, might just have brought the roof in on Jose Mourinho. As it is, the tensions at Madrid remain just beneath the surface but they are there nonetheless, and who know what state this team and its manager might be in by the time they arrive at Old Trafford for the second leg in 5 March?
It was a night when Sir Alex Ferguson got his team right and made some big calls that shaped the game. He did not stop Cristiano Ronaldo scoring once but his team stopped Ronaldo scoring more than once, which given this extraordinary player's record of 183 goals in 180 games is no bad going. At times United defended heroically – that was always going to be the case – but heroic is no good if one tiny error undoes all the hard work.
It only takes one lapse or one rash tackle and the whole performance, built painstakingly over 90 minutes, collapses. The likes of Phil Jones, Rio Ferdinand, Jonny Evans, Michael Carrick and even Rafael da Silva, booked in the first half, but left on by Ferguson, performed with great maturity. Behind them, David de Gea had one of his better games for United.
So too, Danny Welbeck who scored the precious away goal that gives United one hell of a chance of making the quarter-finals of this competition. Not everyone got the chance to cut loose, and Wayne Rooney will face the inevitable criticism for failing to set the stage alight but he was asked to do a specific job on the right side for United which left very little scope to attack.
This was a United team that was without Nemanja Vidic even on the bench, a consequence, Ferguson said later, of his captain only being able to handle one game every eight or nine days in his recovery from injury. Ronaldo came into the away dressing room afterwards to catch up with old friends which would usually have prefaced the jokes about that being as close as United got to him all night. But not this time.
In the first half, Ronaldo was a key threat and on the occasion when United got it wrong, he out-jumped Patrice Evra to head in the equaliser. After the break, United managed to keep him much quieter and, if anything, it was Angel di Maria, on the opposite wing who looked the more dangerous.
For much of the first half, there was hardly room to breathe. Madrid tried to blow United away in the first 20 minutes with many of their attacks coming from the feet of Ronaldo. Rafael dealt with the phenomenon as best he could but he could not stop every attack. Carrick made some crucial tackles around the area, especially one on the excellent Mesut Ozil.
Booked early, and unnecessarily, by a nervous referee, Van Persie had to watch his step. Yet everything that came up to him, he made use of and it was the United striker's flick that allowed Shinji Kagawa a run at goal and led to the disputed corner from which United scored.
That goal showed up the cracks in Madrid. Sergio Ramos, a truculent, complaining presence all night, was too busy trying to get a handful of Welbeck's shirt to prevent the United man pulling away from him nicely and placing a sweet header just inside the post where Madrid had neglected to cover.
It was against the run of play but then United's chances were always going to come on the counter-attack. Welbeck's goal came on 20 minutes and Ronaldo climbed above Evra to score the equaliser 10 tense minutes later. In the interim, De Gea, who had a strong first half, saved from Di Maria and Van Persie stopped a Ronaldo free-kick with his face.
United were still arguing that the ball had gone out of play when Rafael ushered Ozil to the touchline on 29 minutes and Madrid began the move for their goal. For that reason they failed to get across to Di Maria before he picked out Ronaldo towards the back post with an unerring cross. On such small margins do games like these swing.
The Ronaldo effect after half-time was considerably reduced. De Gea made an excellent save with his feet on the hour, scuttling across goal to block Fabio Coentrao's shot from Sami Khedira's ball to the back post.
In that first 15 minutes of the second half, United managed to keep Madrid at bay and perhaps the most telling moment of the game was when Evra found himself running onto a throughball from Carrick with Raphaël Varane in pursuit. The younger Frenchman seemed to foul Evra, and there was no covering defender left, but the German referee waved play on.
On 72 minutes, with both Gonzalo Higuain and Luka Modric on, United broke. Rooney drove forward and picked out Van Persie whose explosive shot was pushed up onto the bar by Lopez. United recycled the ball to Carrick whose header forward beat the offside line, With only Diego Lopez to beat, Van Persie hit his shot into the ground meaning it lost enough pace that Alonso could scoop it off the line.
The introduction of Ryan Giggs drew applause from all around the Bernabeu, a nice moment amid the tension. De Gea saved from Khedira with 11 minutes to go and the door remained locked in the final stages. United have the advantage, one feels, not simply through that away goal but because who knows what state of war Madrid and Mourinho could find themselves in, in 19 days' time?
Man of the match Ozil.
Match rating 8/10.
Referee F Brych (Ger).