There may have been mischief in Diego Simeone’s words but there was truth too. Atlético Madrid’s manager was analysing the Spanish Super Cup first leg against Real Madrid, late into the night. It had finished 1-1 with two goals in the last nine minutes, after a largely uneventful game came to life in the final quarter of an hour. And the turning point, said Simeone as he sat in the press room at the Santiago Bernabéu, had been when Real sent on Ángel di María, “their best player”.

Di María’s future already appeared to lie elsewhere and when Simeone’s words were relayed to Carlo Ancelotti a few minutes later, Real’s manager said: “I think he has forgotten about the Ballon d’Or winner Cristiano Ronaldo and about Gareth Bale, who scored in the final in Lisbon [against Atlético].” The exchange was eloquent, incisive blows delivered with a deceptive politeness. There was an extra layer of meaning in their words. What was happening behind the scenes was played out in the press room.

Two days later Ancelotti admitted that Di María had asked to leave. Usually so calm, he appeared surprisingly tense, a little curt. The following night Atlético beat Real 1-0 in the second leg to take the Super Cup. Di María had been left out of the squad. Asked why, Ancelotti said: “Technical decision.” Then he added: “We didn’t need him.” All round the room, people stifled giggles. Now Di María has gone for £60m. Manchester United have made him the most profitable sale in Real Madrid’s history.

That’s the good news. The bad news is that they will miss Di María, even if some at the club do not think so. Ancelotti certainly will and Simeone probably knew that when he highlighted his countryman as Real’s best player. Man of the match in the Champions League final, the player whose run made the second goal for Gareth Bale; scorer in the Copa del Rey final against Barcelona this season; assist provider for the winner in the Copa del Rey final against Barcelona in 2011; the electric runner who left Carles Puyol doing the splits in the clásico in the league; one of the World Cup’s outstanding performers, a finalist whose team lost the final without him … Di María is the kind of player Real might have signed if they had not already got him.

Last season, no one in Spain provided more assists than he did, with 22 in all competitions. According to Opta, over the last four years in La Liga only Lionel Messi has given more assists. The list reads: Messi 57, Di María 49, Mesut Özil 47. For the second year in a row, Madrid have sold their top assist provider. It is not just Spain: only Messi and Özil have given more assists in any of Europe’s top five leagues since 2011. “Di María is [currently] better than Messi,” Argentina’s World Cup-winning coach César Luis Menotti said this week.

He leaves Real with 36 goals and 72 assists in 190 games. That run in the Champions League final helped deliver the 10th European Cup. “We’ll never forget your zigzag in Lisbon,” Xabi Alonso wrote.

It is not just those headline moments that drew admiration from team-mates, many of whom, like Alonso, were quick to thank Di María. It is what he did for them; it is that they wanted to express support as well as gratitude.

Challenged on his description, Simeone said: “He is the one that breaks through the opposition, tilting the balance of the game, and he makes the other players perform better.” Simeone believed what he said; his appraisal was an honest one.

No one in the team covered the ground that Di María did. He was the man who held it all together, all things to all team-mates: attacker, midfielder and sometimes even defender in one. There are others with his talent, or more, but no one else in the squad has the same qualities. James Rodríguez, the man who will replace him, does not.

José Mourinho, who insisted on Real signing him for €30m (£24m) from Benfica, thought Di María indispensable. Ancelotti did too. The coach described Di María’s work for the club as “fantastic”. Mourinho played Di María on the right of the front three. If he had a flaw, it was that he often lost the advantage he had gained with his speed by stopping to come back on to his left foot. That flaw soon disappeared on changing position.

When Real signed Bale, he occupied Di María’s position. Ronaldo, immersed in his own negotiations over a contract extension, had persuaded a doubtful Di María to stay and a doubtful board to keep him. Had Arsenal not come for Ozil, he might have gone anyway. With Bale struggling for fitness early in the season, Di María played and did very well. Ultimately they could not both play there regularly. There simply was not a space for him.

Di María’s frustration grew and fans were not always appreciative. He did not always think it was fair. On his way off the pitch, having been substituted in one game in January, he grabbed his crotch. He later claimed that he was merely “accommodating” himself. Ancelotti accommodated him on the left side of the midfield three, where he was superb.

Being there suited him: even when he had played on the right for three seasons, his most decisive moments had, curiously, come from the other wing. With the change, he brought the “balance” that Ancelotti talked about and, as Simeone put it, he made those around him better players; 4-3-3 worked. It had worked only with Di María and now he has gone. “We wish him the best,” Ancelotti said. “The club did everything possible [to keep him] but he decided differently.”

Di María would not agree and Ancelotti might not entirely believe his own words either. Simeone seemed to sense that the manager was not on the same page as the president and the board: there was an element of provocation in him declaring Di María Madrid’s best player, a sense of him twisting the knife. Perhaps he knew, or thought he knew, that Ancelotti did not want to lose the Argentinian, but that those above him did.

Top 10 British signings. Photograph: /Guardian

Madrid had offered Di María a contract but he had turned it down and asked to leave. He leaves because he wants to leave, yes. But it is not that simple. Di María was the least well paid of Real’s attacking players and he felt that the salary he was offered was symbolic of the “fact” that some at the club never truly believed in him. They made him an offer he couldn’t but refuse. For two years in a row, they have signed players who occupy his position. First Bale, now Rodríguez.

Menotti’s comment about Di María being better than Messi came in this context. The former Argentina coach was critical, seeing Madrid’s manoeuvrings as an attempt to force out Di María. “What they have done to Di María is an injustice,” he said. “They have signed James Rodríguez to sell more shirts. He is a marketing product.” The headline on an editorial in the sports newspaper AS declared simply: “Because he doesn’t sell shirts”.

That may be too facile but there is a sense that Di María’s face did not fit. There was little glamour, little stardust, no matter how good he was on the pitch. Certainly, that is the way he feels: if they had really wanted him, if they had really valued him, they would have offered him a deal he could accept. He had earned it on the pitch. Di María was never a player who enjoyed presidential predilection or protection; if team-mates were sorry to see him go, the club president Florentino Pérez would not have shed a tear. The impasse had already been reached and that money was instead used to pursue a new signing, someone the president could feel was his own.

There was something inevitable in the turn to Rodríguez after his performances in Brazil, a player in whom there had been no sign of interest before. It is a path not open to Di María: he could not be the discovery of the summer. The season Di María had, World Cup included, was the kind of season that awakens Madrid’s interest in players, but fault lines had opened up, you can’t sign who you already have and some of the seduction comes in the signing itself: in the presentation. Being new is a virtue with a value. You don’t create excitement or fill a stadium with a contract renewal.

While 83% of supporters in one poll said that, yes, Real do need Di María, last season they chanted at the president not to sell Ozil and that did not turn out too badly: when Madrid collected the 10th European Cup, no one was complaining any more. Casting the mind further back, the lesson is a different one of course: other sales have bitten them badly. The words Claude and Makelele still haunt them, but this is a far stronger, hungrier squad than it was then.

There is also an economic reality and it is a basic one, even at Real: if you spend a lot, you must recuperate something. As it turns out, they have recuperated a huge fee. Real’s net spend is almost zero and they have a new galáctico, plus Keylor Navas and Toni Kroos too. A sale that many criticised now appears logical, at least on one level. Real have effectively upgraded: Rodríguez for Di María. The question of course is whether it is an upgrade at all.