Manchester City have lost out in the Champions League under Pep Guardiola in the last two seasons because key moments have gone against them.
The best team in England have shown that over 38 league games but in two knockout ties they have gone out to English opposition as a result of either not getting the breaks or not responding to not getting the breaks, or both.
At the Bernabeu, they stood strong (enough) when Real Madrid took the lead against the run of play and worked their way back into the game. It felt like a coming-of-age performance from this team in the competition that has given them the most pain, and the one in which has become their priority for the remainder of this season.
At Old Trafford, the collective behaviour of the team in the minutes around United's opening goal should concern Guardiola for the return game with Real.
It may or may not have been a free-kick on Bruno Fernandes, City can't control that - but they can and need to control what follows.
Fernandinho led a flurry of blue shirts to Mike Dean to angrily protest the decision, and the captain was duly booked. Sergio Aguero and Ilkay Gundogan then failed to track Anthony Martial and Ederson wasn't set properly to keep Anthony Martial's shot from squeezing under him and into the goal.
Before City had kicked off, Rodri, City's holding midfielder, had been booked for protesting about the goal to Mike Dean.
Guardiola has been guilty before of not keeping his temper - his red card in the second leg of the quarter-final against Liverpool in 2018 ended any faint hope City had of completing a comeback - but he needs his players to do better.
The free-kick may have been unavoidable but the goal conceded and the yellow cards for players in two key positions were.
There were positives in the hour that followed. The team didn't concede another goal shortly afterwards as they have done in the past - even if they did look rattled until the half-time break. And Rodri and Fernandinho were not sent off so the yellow cards did not prove more costly.
But City were still weakened by unnecessary losses of composure and concentration and there is no guarantee that better teams than this United one - and let's face it, they're not great - will take more advantage of the opportunities they are presented.
As Guardiola tries to get his men fighting fit mentally as well as physically for the Champions League tests they expect to be ahead, those two first-half minutes at Old Trafford showed that there is still work to do.