Chelsea and Manchester United managers were together at Barcelona, where closeness and respect grew strongly, but their different paths since will be on display in Sunday’s showdown

When Louis van Gaal took the manager’s job at Barcelona in the summer of 1997, he was a year early. Originally, the idea had been to go to Catalonia for a season, familiarising himself with his surroundings, the league and the language, plan for the club’s future and then take over the following season. Instead the process was accelerated by a president under pressure and with an eye on looming elections. Bobby Robson was shunted out of the way, becoming a director of signings who made no signings, and Van Gaal moved in.

“My place is on the bench,” Robson pointedly remarked at the end of the 1996-97 season, having won the Cup Winners’ Cup and Copa del Rey. By then, he knew he would be bundled upstairs. He had found out in late April when Barcelona played at Fiorentina. Amid the rumours he had confronted Josep Lluís Núñez, the Barcelona president who was this week found guilty of bribing a tax official and who back then publicly and cynically claimed to be the only one standing by Robson.

When he found out, Robson was furious. And so was his assistant: José Mourinho. “I’m leaving,” Mourinho told him. Robson, though, could see that leaving would not be good for the young man he had taken under his wing. “No, stay,” he replied.

Mourinho approached the new manager and told him he would like to continue at the club. When Van Gaal asked why, Mourinho replied he was sure he would learn from the Dutchman. It made sense for Van Gaal, too: here was an assistant manager who spoke Spanish, knew the players, and came highly recommended by Robson, so Van Gaal told the president he wanted the Portuguese to continue.

“Mourinho scouted the opposition and provided reports that were first class,” Robson recalled. Under Van Gaal, his responsibilities would grow further. And the following spring, he was asked to stay for another year. “I’m delighted he said yes,” Van Gaal told the media.

“I developed a lot of my own ideas. Louis is Louis and Mourinho is Mourinho, there is no comparison, but I would be lying if I said I didn’t learn from him because I did,” Mourinho said of the man he will face on Sunday, for only the second time in his managerial career, when Manchester United play Chelsea. “He is honest and pragmatic.”

As for Van Gaal, he was impressed. “José was a little bit arrogant but I like that. I like people with a high opinion of themselves,” he said.

Van Gaal liked that Mourinho argued with him; that he disagreed, that he said what he thought, not what he thought the manager wanted to hear. Others did not have the nerve and, as a result, contributed less. Mourinho was young and still dependent, but he was not afraid to contradict the man in charge.

He was also different to Van Gaal. While the coach was not always popular, Mourinho’s relationship with the players was closer, even if some came to suspect what they said had a habit of getting back to the manager. “[Van Gaal] got mad at us a lot. Everywhere: in training, in matches. He was very demanding,” recalled Simão. “[Whereas] Mourinho was very relaxed, always making jokes. He was very attentive.

“He obviously knew about football and [he] spoke well but he wasn’t the Special One yet,” Luis Enrique told FourFourTwo. “He had a good relationship with Van Gaal and was very clear with us. I liked him.”

Mourinho was struck by the way Van Gaal controlled every detail and would come to do the same himself, right down to the little notebooks for which the Barcelona manager became (in)famous.

“With Van Gaal the practice sessions were set out already. I would know everything we were going to do in training beforehand, from the aims to the exact time each exercise was going to take place,” he said before these two last met, in the 2010 Champions League final. “Nothing was left to chance; everything was programmed to fine detail.”

And, although he had the charm Van Gaal did not always display, while he was open and funny, Mourinho embraced the discipline the manager demanded. He took it all in, always looking and learning – about human relationships as well as tactics.

“I watch[ed] Mourinho every day for a year,” says Hristo Stoichkov. “Mourinho was looking every day, reading the conversations, the attitude of the players, the sessions. He is the typical guy who watches everything – changing room, bus, hotel. Everything is under control. Everything. That’s the reason why he has a tough character.

“He liked everything to be 100%: good discipline, good organisation. One person late to training [is a] disaster, [there’s] no respect for the [other] players. I learnt a lot of things with him. He likes everything, step by step, [to be] on top of everything. I could see that back then.”

During some games, Mourinho sat high in the stand, reporting back to Van Gaal on the bench. He began to take training sessions himself and one day Van Gaal told him to take charge of the team in a Copa Catalunya game: he trained them, picked the side, and took the press conference.

“He carried out the analysis of opponents and he did it very well,” Van Gaal recalled. “And I did something I don’t do often: I let him coach because I could see that he had talent.”

Time has taken them in different directions. Perhaps that was inevitable. Van Gaal arrived at Barcelona because the club saw in him the latest incarnation of the Dutch school, a man who had won the European Cup with Ajax and was committed to a footballing philosophy they wanted to share. Mourinho already saw things differently and said so.

He called Van Gaal “pragmatic” but Van Gaal clung to a stylistic ideal. He talked about the need to entertain, to attack, to play in a particular way. When they met in the Champions League final, Van Gaal at Bayern Munich, Mourinho at Inter, the former was quick to note: “Mourinho is more defensive.”

Yet Mourinho described Van Gaal as the best coach at the World Cup this summer and there is warmth between the men who were near neighbours in Sitges, on the coast just outside Barcelona. Back in Catalonia, they talk about Mourinho, the assistant coach, as a man who had “enormous respect” for Van Gaal. And they talk about Van Gaal as a man who was “devoted, absolutely devoted” to Mourinho.

Mourinho insisted: “There will always be a fantastic relationship between us. I like him a lot and I know he likes me a lot too.”

At Barcelona, Van Gaal took his role as a mentor seriously, becoming almost as paternal as Robson had, and takes pride in Mourinho’s success, for all that they have embarked on different paths. He could see something special in Mourinho and he did not want him to sell himself short, as if he ever would. The first time Benfica expressed an interest, Van Gaal told him: “If they want you as an assistant coach, say no. If they want you as a manager, go.”

In 2000, they did. And so did he. Van Gaal told his Barcelona players: “A great assistant coach has just ended his career ... and a great coach has just begun his.”