At 9.30am, the same time they started serving breakfast at Atlético’s, Diego Costa walked into a Majadahonda clinic across the other side of Madrid, but he wasn’t going to be kept from them for long. He had barely been in the country 15 hours, touching down just before five on Friday, and he was only in the clinic 60 minutes or so, most of it spent getting reacquainted with familiar faces. There were no photos, shirt off, suckers on, thumbs up, and when he was asked if he had passed his medical he pointed to the doctor and said “I don’t know, he knows”, but he was beaming. He stopped for a snap with a Málaga fan nursing a broken and bandaged arm and leg, like something out of a cartoon, then climbed into the car and set off 33km round the M40.

Outside the Wanda Metropolitano some were still drinking hot chocolate and eating churros, offered in an attempt to get them there early ahead of the 1pm kick-off on Saturday, while others had moved on to beer. Not far away lay the plaques dedicated to Costa and everyone who had played for Atlético 100 times; he hadn’t seen his yet, but fans gathered taking photos. Inside, friends waited. As he had touched down the day before at Barajas – the only airport named after a member of the A Team – Costa said he was coming “home”. Tiago was at the gate, Diego Godín greeted him in the tunnel – “Welcome, my friend. You’re home now,” he tweeted – and Filipe Luís was delighted too. Afterwards, he said: “I’m immensely proud Diego has chosen Atlético.”

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When Costa appeared in the directors’ box a few seats along from Fernando Torres, there was applause. He waved and when the goals went in during a very Atlético 2-0 win, he celebrated. Below, Diego Simeone, the man in black who’s wanted him back since the day he walked away, ordered the team and choreographed the crowd, later likening the Metropolitano to a “roman circus”; Koke, who said he and Costa had a “special understanding”, played alongside Gabi, his captain; and in the corner stood someone he knows too well, the man he admitted being “scared” of and whose job it is to beat him into shape: hyperactive sadist and fitness coach Profe Ortega.

It still wasn’t official – it still isn’t official, in fact, and it will be January before he can actually play – but Diego Costa was back. Time to get the old gang together.

The new gang too.

Costa finally returned to Atlético Madrid for a total of €65m this week and while much remains the same, while his return partly represents an attempt to recover what they lost when he left, to go back to what they know, while it is only three years since he was here, it is not exactly as it was the day he went. This season less than ever before. They are in a different home, for a start. Tiago is not a team-mate now, he is a coach. And below him on Saturday, the men who scored were Antoine Griezmann – Atlético’s star – and Yannick Carrasco, neither of whom were there when he was. Sitting to his left was Torres, while Luciano Vietto started and Kevin Gameiro came on. Like Mario Mandzukic and Jackson Martínez, those three came partly to replace him, but never really could. Others have gone not to return: David Villa, Arda Turan, Thibaut Courtois, João Miranda. More importantly – and this was what stood out this weekend, further confirmation of a new trend emerging in Simeone’s seventh season – some may be beginning their farewells. A shift has started.

On Saturday Atlético’s manger made five changes from the team that played Athletic Bilbao in midweek. Just as he had made five between weeks one and two, four after the game against Valencia, three after Málaga. He has made at least two changes every game this season. Of the outfield players only Koke and Saúl have started every match. None of which would be particularly unusual for most coaches – rotation is hardly revolutionary – but for Simeone it stands out. The year Atlético won the league, nine players started at least 32 of the 38 league games and they reached the Champions League final exhausted. Last season, eight started at least 29, despite the fact that, Griezmann apart, Simeone never seemed entirely convinced by his strikers or sure which wide/creative player to include. By contrast, this season 16 players have at least two starts – after just six games.

It is not solely circumstantial, it is a choice – even if it is one that was partly forced upon them. And that’s a change for a manager who previously sought stability, a comment too on the way Atlético have grown. “I want everyone to feel a participant,” Simeone said. “It is my challenge to ensure that no one is more important than the team.”

Facebook Twitter Pinterest Diego Costa attends the match against Sevilla. Photograph: Ballesteros/EPA

Costa will certainly take them onwards and the excitement among the fans is overwhelming but Simeone said: “Not signing players made us take a step forward.” He had a point, too. The transfer ban shifted the focus; to the players they already had. Not selling was Atlético’s ‘buying’, with only Theo Hernández slipping away. Antoine Griezmann was vital but it was others too. Renewals became vital and so did opportunities; not least because those players are good enough now; they have grown. Asked why he had changed, Simeone replied: “Time.” His response contained a simple truth. “Time allows you to evolve,” he said. It allows players, manager and the club to evolve.

Why has he started rotating? Because he has had to and, more to the point, because he can. The squad, steadily built and with players emerging from the youth system, permits it. “Internal competition” was a phrase Simeone repeated often on Saturday and it is fierce now. He said it “tears my soul apart” to have to choose, especially when it comes to the defenders, so high is the level, so deserving the players. Rotation reflects that. It also reflects something deeper. Indeed, it is tempting to see this more as the beginning of a transition. The ideas remain steadfast – in fact, he has a tendency to revert to type, and Costa partly reflects that – but this may be the start of a second Simeone team, a second era, a new generation, even if it includes the return of a striker who helped define that first, miraculous title-winning success.

Saúl and Koke are both youth-team products, aged 22 and 25 respectively. For the first time in over a decade Gabi, the captain so close to Simeone that he spent one game last season with an earpiece in when his manager was suspended, has been left out of the team for two games in a row. The man who made 35 starts in 2013-14 and 33 last season has already sat out for three of six this season. In his place has come Thomas Partey, who didn’t start on Saturday but has started four times. At the back, Juanfran – a committed Cholista – has started only half the games. Against Sevilla even Diego Godín was rested, missing his third league game. In his place was Lucas Hernández, 21, making his fifth start. “I spoke a lot to Lucas and Thomas especially in the summer,” Simeone said. “They’re young and I said that they maybe hadn’t had continuity because I didn’t put them in or they didn’t always take advantage.”

At the end of last season, when the thunder rolled and Atlético bade farewell to the Calderón, knocked out of the Champions League by Real Madrid, there was a sense that something was coming to an end, maybe even that it was all over for good, time to walk away. They were going to a new stadium which provoked anxiety as much as excitement, Simeone’s future was not secure, and the fear was they simply could not keep this up. There were many questions and one very simple problem was floated: age. “For six years we have been giving our lives,” Simeone said. “It’s a pity that years pass and we can’t clone the players. Maybe next year they won’t be at the same level, I hope they can be. We have to clone Gabi and Godín: they give us life.”

Twice Simeone returned to the theme: if only we could clone them. You can’t. But a few weeks later Simeone announced, to everyone’s relief, that he was staying, “because this club has a future … and the future is us.” Soon he extended his contract. He had seen Atlético were making good on their promise to back him – Vitolo and Costa represent a huge outlay – and he saw a future, the chance to rebuild and restructure. These rotations are the start. You can’t clone, but you can protect and prolong. You can also develop. And, with time, replace.

Facebook Twitter Pinterest Saúl in action against Sevilla. Photograph: Shot For Press/Action Plus via Getty Images

“No one is a starter,” Filipe Luís said. “The players know that even if they don’t play today, they have a chance in the next game.” So far, so standard. But more telling was what came next: “Every day it is harder,” he continued. “You see the growth of players, like we did when Kun [Agüero] came at 16: Lucas, Thomas, Correa … they make a case every game. The kids are coming through and they’re hungry; they’re putting pressure on us and we know that we can’t let up in a single training session. If they maintain this ambition the team will benefit. I’m trying to keep up with Lucas; I learn from him now.”

He described Costa as “one of the best three strikers in the world”, “a contagious” player who “has won everywhere he has been” and whose arrival represents a “big step”. Yet even without him, Atlético are second, unbeaten in six having begun with three away games in a row while the Metropolitano was readied. They have already been to San Mamés and Mestalla and on Saturday it was unbeaten Sevilla they defeated, with a performance that, while not sparkling, was very like them, the next generation doing what the former generation always did. New Atlético, same old Atlético.

It is too early for conclusions of course but Atlético are convincing and so is the new policy, used by many managers but not really by Simeone before. “In the end, the pitch talks,” he said. “All the coach does is listen to the pitch.” Even on the day when attention was drawn to the directors’ box, to the homecoming of the man who wasn’t out there yet and won’t be for three more months.

Talking points

• It was the 85th minute of the weekend’s best game late on Sunday night – a frantic, fun, open match with 31 shots and four goals so far, two each – when Valencia, who twice led only for Real Sociedad to swiftly equalise, broke at speed, just the way their ultra-demanding manager likes them to. Up the pitch they zoomed, Guedes racing away to find Simone Zaza, bombing up alongside, for a superbly taken first-time winner, as exhausted team-mates tried to catch them. Which was when Marcelino felt his hamstring go, pulling up and holding the back of his leg and having to hobble away down the tunnel at full-time, happy but hurt. “I felt a pull you can’t imagine,” he said afterwards.

None of which would be especially unusual, except that Marcelino is a manager, not a midfielder. When the goal went in Valencia’s coach leapt from his seat, much as he leaps from side to side all game long, and pulled a muscle. It is not the first time either – a few years ago, he had to momentarily halt a press conference with an attack of cramp. “I’m getting older: there are certain situations I should avoid,” he said. “But I’d rather I was crippled than have any of my players injured.” Unbeaten in six, having played Atlético, and gone to la Real and Real Madrid, he has Valencia fourth, a proper team with a proper manager at last.

Facebook Twitter Pinterest Simone Zaza celebrates with Santi Mina after his winner. Photograph: Juan Herrero/EPA

• “He asked me how old I am and whether I was on loan from Manchester City,” Pablo Maffeo said. “He’s a nice person.” The Girona player should know: he and Leo Messi had plenty of time to talk after he was asked to do a man-marking job on Saturday night. Everywhere Leo went, Pablo went too. As they came off at half-time they walked together, chatting behind their hands, but Messi had clocked it from the start. They were only finally parted late on when Maffeo, on a yellow card, was withdrawn. It had worked. Well, sort of: Messi didn’t score – and after nine goals in five league games that counts as a success – but by then, the game was lost. Girona scored twice, Barcelona scored once, Barcelona won 3-0. Two own goals and a third from Luis Suárez did it. As for Maffeo, he didn’t even get Messi’s shirt: a mate had made him promise to get Marc-André ter Stegen’s instead.

• Dani Ceballos was busy writing his name on his hand. On his first start for Real Madrid, he scored two neat goals to clinch a 2-1 win at Alavés. Much of the focus was on Madrid missing a lot of chances again, which they did, but they were not great and it could have gone the other way too: Pedraza twice hit the post.

• Espanyol, Celta and Getafe all scored four, Málaga and Athletic scored six between them, three each, and there were five between la Real and Valencia as La Liga produced another boring, predictable round of games. Mind you, set plays did account for quite a lot of them, Villarreal manager Fran Escribá insisting “we can’t go on like this” and midfielder Samu Castillejo calling it an “issue” after they let in three more in a 4-0 hammering at Getafe via that route – and that’s six of the nine they’ve conceded this season. It turned out the club agreed they couldn’t carry on like that: Escriba was sacked on Monday morning. As for Eibar, three first-half in-swingers cost them three goals against Celta. “We’ve conceded 15 goals this season, so it’s clear what out problem is,” Pepe Mel said after Espanyol defeated Depor.

• Málaga were 3-1 down with nine minutes to go against Athletic, and Twitter parody account Sheik Al-Thani was clicking on compose, axe hovering over manager Míchel, but the fans kept going and so did the team. Iker Muniain had been superb – again – and Iñaki Williams scored twice and might have got a third, but Málaga weren’t done. They scored twice to get their first point of the season, six weeks in. “It doesn’t fix much,” Míchel said, “but it does fix our hearts.”

Results: Atlético 2–0 Sevilla, Alavés 1–2 Real Madrid, Málaga 3–3 Athletic, Girona 0–3 Barcelona, Espanyol 4–1 Deportivo, Getafe 4–0 Villarreal, Eibar 0–4 Celta, Las Palmas 0–2 Leganés, Real Sociedad 2–3 Valencia. Monday: Betis-Levante.