MARCH 14 ― Marcelo Bielsa, the eccentric Argentine football manager who was last seen with Lazio (for two days) and is credited with inspiring the methods of Pep Guardiola, Mauricio Pochettino and many more, once made an utterance which perfectly encapsulates the frustrations of sporting coaches everywhere.
“If players were robots,” he complained, “I would win every week.”
Those words came to my mind on Monday night, when I watched Chelsea overcome Manchester United to earn a place in the FA Cup semi-final, because visiting boss Jose Mourinho's finely planned strategy was undermined by the players he had entrusted to carry it out.
The big question for Mourinho was how he could try to hold back a Chelsea team which is full of confidence and handed his team a 4-0 Premier League battering at Stamford Bridge earlier in the season.
Mourinho is renowned, of course, as one of the greatest tactical brains in the game, especially from a defensive viewpoint, and he certainly came up with an innovative plan for this game with the intention of stopping Chelsea's front three of Diego Costa, Willian and Eden Hazard.
Watching the start of the game, it took a bit of time to work out how United were playing, because their formation certainly didn't at all resemble a conventional flat back four or line of three.
Instead, they were only really playing with a back two, with Marcos Rojo and Chris Smalling holding the fort with their attentions focussed on Costa.
Ahead of them, Matteo Darmian and Phil Jones were neither playing strictly as defenders nor midfielders, but somewhere between the two as they carried out man to man marking jobs on Willian and Hazard.
The team's only width was provided by Ashley Young on the left and Antonio Valencia on the right, with central midfielders Paul Pogba and Ander Herrera stationed behind the front two of Henrikh Mkhitaryan and Marcus Rashford.
This novel approach was a primarily defensive strategy, essentially telling Chelsea: you only have three attacking players who can damage us, and we are going to take them out of the game.
And it worked well, with playmakers Hazard and Willian denied the space they crave to create, meaning that Costa was starved of service, and Chelsea struggled to exert consistent attacking pressure during the opening half hour.
The only exception came when Hazard produced a brilliantly swift turn to create space for himself, resulting in a deflected shot which drew a fabulous save from David de Gea, who then did even better to keep out Gary Cahill's low shot from the resulting corner.
Other than that United were comfortable, without exerting any significant attacking pressure of their own, until Mourinho's carefully laid plans were ruined ten minutes before the interval when Ander Herrera was sent off after receiving two yellow cards for fouls on Hazard.
And this was where Bielsa's frustrations about the imperfections of players first came to mind, because Herrera had no need whatsoever to get himself sent off.
The second yellow card, it's true, was rather harshly awarded and United will feel aggrieved at the decision. But Herrera did not need to force the referee into making a decision at all, because his foul on Hazard was made in a harmless position where the Chelsea player was not really going anywhere.
By making the challenge when he was already on a yellow card, Herrera was really just inviting the referee to overreact, and that's exactly what happened
Now United were really under the cosh, with Mkhitaryan making way for Marouane Fellaini to retain numbers in midfield while leaving Rashford on his own up front.
That didn't change their defensive approach, but it did mean they would struggle even more to relieve Chelsea's stranglehold on possession, and the amount of running required, while retaining positional focus as well, was always going to be very demanding.
And, indeed, it took Chelsea less just six minutes of the second half to make their extra man count, as N'Golo Kante beat de Gea with a fine low strike from the edge of the penalty area.
But once again, the non-robot-like nature of footballers played its part, because Kante was only able to get his shot away so cleanly because Pogba, perhaps assuming his international teammate couldn't cause that much danger, was a little lazy in closing him down.
If Pogba had been one of Bielsa's robots, he would have shut down the space and either blocked Kante's shot or prevented him from releasing it in the first place.
Instead he eased off, just for half a yard, and that was all the space Kante needed to try his luck ― especially as Herrera, who would have probably been in the vicinity to make a challenge, was no longer on the pitch.
And that, essentially, was that. United only had one real chance to equalise, with Rashford having his shot well saved by Thibaut Courtois, and Chelsea advanced into the semi-final with a goal which hadn't entered into anyone's plan for the game ― and it was all because of human imperfections.
* This is the personal opinion of the columnist.