Iván Zamorano smiles and lets out a little laugh. “The idea came about because the best in the world had arrived,” he says with a knowing glance. “I had to hand the No 9 over to him.”

Zamorano was at the top of his game when Ronaldo joined him at Inter in the summer of 1997. He had won the Copa del Rey and La Liga with Real Madrid, picking up the Pichichi prize for top scorer in his last season in Spain before moving to Inter, where he was well on his way to becoming a legend. But he was humble enough to know he had no choice. Zamorano says he “did not play with many Brazilians, but I played with the best of them all: Luís Nazário de Lima – among those I played with, Ronaldo is the greatest.”

Speaking in São Paulo, where Zamorano is covering the Copa América for the American Spanish-language TV channel Univision, his praise for Ronaldo might be construed as merely saying what the locals want to hear. But there is not a hint of doubt in his voice. “The only thing missing from him was what I did best, scoring headers. He didn’t get many goals with his head. Everything else, complete: left foot, right foot, power, ability, magic! He had everything. In training it was better than the weekend. He was a phenomenon.”

With Ronaldo and Roberto Baggio hogging the No 9 and No 10 jerseys at Inter, the Chilean had to improvise. “The sporting director, Sandro Mazzola, told me to pick a number that added up to nine. I said: ‘Can I add a plus sign?’ He told me not to. I said: ‘How come? Request permission.’ I spoke to the president, Massimo Moratti, who asked the Italian federation. So I played with 18, 1+8, and I didn’t lose the No 9.”

“That was a great Inter,” he says. “We played with heart. We won the Uefa Cup. We were in two finals; we won one and lost another. Most importantly, we created the essence of a club, something that belonged to the fanbase. Playing with Ronaldo, Vieri, Baggio, Zanetti, Bergomi, Paul Ince...” He tails off, but the reverence is clear.

Zamorano in his Inter shirt in 1998. Photograph: Stuart Franklin/Action Images

Despite scoring 34 goals in 69 games for Chile, Zamorano never won a trophy with the national team. Over an international career that spanned three decades, he often led the line with Chile’s other star, Marcelo Salas, yet the players behind the front two were not quite at their level and success eluded them. Chile have been blessed with a more complete set of players in recent years and Alexis Sánchez, their current leading man, has overtaken both Zamorano and Salas to become the country’s all-time top scorer.

Coming off the back of a difficult season in Manchester, Sánchez has recaptured his form at the Copa América with two goals in his first two games. “Manchester use him in a different way than he is used for the national team,” says Zamorano. “When he pulls on the Chile shirt, Alexis always responds. For Chile he defends less and has more freedom, but in Manchester he has to track back.”

Unlike a lot of United fans, Zamorano believes Sánchez will eventually enjoy success for the club – just as he has in two other red shirts. “I’m convinced that at some point Alexis will blow up in Manchester and will be the same player he was at Arsenal and the same player who impresses for the national team. It takes time. The first year at United was difficult, with many injuries and pressure. It will take a little time for him to explode.”

After winning the Copa América in 2015 and 2016, Chile failed to qualify for last year’s World Cup. But they are through to the Copa América quarter-finals and Zamorano has seen some progress in their games so far in Brazil. “We arrived in silence,” he says, “because we didn’t play well in the friendly matches before the Copa América. Even Reinaldo Rueda, the coach, was being questioned a bit. But I think that in the match against Japan I saw moments [worthy] of a two-time champion. I saw moments that give us hope that Chile can be a protagonist.”

Yet Zamorano has been unimpressed by the style of football on show in the tournament. He has high standards, having played in some wonderful attacking teams – including the Real Madrid side that won La Liga in 1994-95 playing a swashbuckling brand of football under Jorge Valdano. Zamorano says that was the best season of his career. “I was top scorer, champion, best player. It was with Jorge Valdano – a coach who was very important to me. He had been World Cup champion and a coach who makes you grow as a player.”

Valdano, writing in his column for El País in Spain, has also bemoaned the style of football on show at the Copa América, complaining that South American coaches spend too much time searching for “equilibrium” – a euphemism for dour, defensive football – “waiting with ten men [at the back] and attacking with one”.

Zamorano celebrates as Chile go through to the last-16 of the World Cup in 1998. Photograph: Russell Boyce/Reuters

Zamorano’s complaints about the tournament echo those of his former manager. “There are interesting things and not-so-good things,” he says. “Coaches need to risk a little more so we can see better football. The teams play very defensively. Football lovers want to see a game with more goals, more great games. There are many teams that try to play better than others. Colombia is one that tries to play. Chile try to play.”

“Brazil try, but they do not have the ability to make a difference on the pitch. There are now questions about Brazil not having Neymar, but when he got injured some people said: ‘Brazil play better without Neymar.’ I don’t see it like that. On paper, we see that some teams are better than others, but today you don’t win anything with your shirt or with history.”

Brazil may or may not miss Neymar but Zamorano is certain that none of their current players measures up to his old teammate Ronaldo. Without the injuries, could he have been the greatest of all time? “Ronaldo is among the best. Pelé, Maradona, Beckenbauer, Cruyff, Messi, Cristiano, Ronaldo ... he’s on this list of the 10 greatest players ever. Injuries are something that no player wants, but when I see a player who has the ability to recover from what happened to his knees, he deserves credit. A lot of people said he didn’t work hard or have that desire. But I was close to him at the time of his knee injury. He said: ‘I’m going to recover.’ He worked like nobody else and came back even better.”

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