The day Ricardo Carvalho arrived Real Madrid fans tapped their watches and tutted. You are late. The question was whether he was too late. The answer, many feared, was yes. He was the right man in the right place at the wrong time, no longer what he was – or so they thought.

Instead he has proved a revelation – the second-best defender in Spain, according to the Castrol Ranking. Informed of the stats at Madrid's Valdebebas HQ, he smiles a little embarrassed. And yet he is not surprised. "I knew," he says softly, "that I was ready." Carvalho was ready for Madrid once before, seven years ago. The deal was virtually done, Europe's best defender on his way to Europe's biggest club. Porto had just won an astonishing European Cup under José Mourinho and, as Carvalho puts it: "We [all] felt it was the right time to leave."

Madrid called. But amid arguments over fees and commissions the deal collapsed and Carvalho went to Chelsea instead with Mourinho. "Madrid were more interested and at first we talked to them more," he says. "But the clubs did not reach an agreement and then Chelsea came in. It was about the clubs, not about me."

Last summer, at last, Carvalho did move to Madrid. But six years had passed – six years Carvalho had spent in London, winning two league titles; six years Madrid spent ploughing through 13 centre-backs, signing eight of them for ¤136m (£120m) and failing to win a single Champions League knock‑out tie. Carvalho's imminent arrival no longer provoked the excitement of 2004. He was getting on, had knee troubles and muscular problems. He had missed at least 16 league games in each of his last three seasons. A fee of ¤8m was even not that cheap.

"I can understand why some criticised the move. I was 32 and I'd been at Chelsea a long time," Carvalho said. "I had a physical problem, which started because I was not given time to recover fully. I was out for longer than is normal for a muscular problem. There was pressure, I wanted to play and I got injured again. It was not properly healed and I had a relapse.

"But I was convinced I'd succeed. I knew I'd play well here. It's a different game and I wanted to prove I was in shape physically and mentally. It would have been easy to stay at Chelsea, where people respected me and moving on meant starting over again. But I needed a change, the challenge — and it was Real Madrid. During the last few years at Chelsea I wasn't so happy; I felt saturated. I needed to try something different, get some impetus. I'd become too comfortable. That's not a good thing. I had to show I was still a good player."

Mission accomplished. Madrid have conceded only seven league goals at home. At the other end Carvalho has scored three times, twice opening the scoring. He has the best shots-per-goal ratio in Spain – "I'll have to stop shooting to preserve that one," he says – and fitness fears have been unfounded. He has played 25 of 30 league matches. Under familiar management he has helped Madrid into the Champions League quarter-final for the first time in the six years since that first attempt to sign him.

The challenge now for the Portuguese defender and Mourinho is to win a second European Cup together. In the interim Mourinho has won it again, with Internazionale last year while the defender lost the 2008 final – a memory that still stings.

"José changed a lot at Porto and very quickly. You could see his methods were good immediately. The players were forced to adapt – we had to change the 'chip' – but it worked and he convinced us. But the truth is that in 2004 our aim was just the last 16. When we beat [Manchester] United, we thought we could win the competition. After winning there we couldn't go and lose to Lyon or Deportivo [La Coruña], with the greatest respect to those teams."

Winning the competition was Chelsea's obsession, too. Perhaps they would have done so if Roman Abramovich had not fallen out with Mourinho: could that have been their gravest mistake? "Well," said Carvalho, incredulously, "the truth is, the closest we got was after he went. It was incredible that we lost. Cristiano [Ronaldo] missed a penalty, Ash[ley Cole] scored. United had to score twice and we had to miss. You think: 'It's ours, this is it.' We were ready to celebrate. And then.

"John Terry missed. Suddenly it was over. But I was so impressed with John. He is a classic English centre-back, so strong, such character. He was angry and crying like all of us – but he didn't hide away in his room. He looked dead but he was there for us. If that had happened to me, I'm not sure I could have done the same. That was incredible."

Talk of Chelsea draws a smile, a reunion appeals. Chelsea-Real Madrid: the dream final? "Definitely." Possible, too. "I talk to the Chelsea players," Carvalho says. "Whenever they say they've had a bad game, I say: 'Nah, you're strong still.' They're the best team in England and I know what it would mean to them to reach the final."

For Madrid, a club whose identity is rooted in the European Cup despite not winning it since two years before Carvalho should have joined and eight years before he actually did, the urgency is even greater. "Chelsea is different, they have ambitions to win it but Madrid have lived it before and want more and more. We have to get into the habit of winning too. It's palpable what this competition represents for Madrid, what success does."

First, though, it is Tottenham Hotspur. On Monday night Mourinho will hand pieces of paper to every player containing details on the man each one is up against. "You can read it in bed if you want," Carvalho says with a grin, as yet unsure if his will say Peter Crouch or Jermain Defoe.

"They're both very good but very different and we'll be forced to adapt accordingly. Against Crouch we can play higher because he is not so dangerous on the shoulder, while Defoe is quicker behind you." So, which would he prefer? "I don't mind. I'm not worried about them – so long as I'm fit, strong and playing well."

He is. Six years later Madrid fans can vouch for it.