Defending champions Chile got off to what looked like a flying start in defence of their title. But a study of the game, rather than just the 4-0 scoreline over Japan, is rather less comfortable for Chile coach Reinaldo Rueda, who at times looked like a worried man on the touchline.

The causes for concern are genuine and won't be papered over by victory against a novice Japan side. Chile still have individual talent, and in flashes, they recall the title winning teams of 2015 and '16; There are moments when they throw men forward and make the ball fizz, with their rampaging attacking full-backs a source of danger. The best example was probably the second goal, where Arturo Vidal, Charles Aranguiz and Eduardo Vargas combined at pace, played out to right-back Mauricio Isla, whose clever pull back was turned in at the near post by Vargas. It was vintage Chile -- but it is questionable whether the team can produce enough of it to put in a serious challenge this time round.

In the race between time and the athlete there is only one winner. And this is essentially the same side with it core of golden generation players that won the title in New Jersey three years ago. Rueda has foolishly been put under intense pressure for short-term results by the local press and public. Rebuilding always comes at a cost, and without the tranquillity to do it -- and with a dearth of new talent coming through -- Rueda has stuck with the old guard, and a team with an average age of over 30.

The high press style of the 2015-16 side requires constant running. The Chilean side - which ran out of steam on the road to Russia 2018 and failed to qualify - are no longer able to retain a stranglehold on their opponents for a full 90 minutes. Rueda recognises this. It is reflected in the three changes he has made to the 2016 side. One, the replacement of keeper Claudio Bravo by Gabriel Arias, is down to internal dressing room politics. Guillermo Maripan has come into the centre of defence in place of Gonzalo Jara because he brings badly needed height to a team that can no longer press high for the full game.

Finally, central midfielder Marcelo Diaz has lost his place to Erick Pulgar. This is significant because Diaz, a fine midfield organiser, is the man to pick the vital first pass forward. Pulgar lacks this talent. But his height is useful - as he showed heading home the opening goal from a corner. And he is much better defensively - and a team that throws two veteran full-backs forward leaves plenty of space behind.

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Despite his presence, Chile had plenty of defensive problems. They can no longer stay compact. Huge gaps open up between their lines. The two late goals give the scoreline a deceptive appearance. Japan missed five clear chances - most of which fell to rookie centre-forward Ayase Ueda. Had Leicester City's Shinji Okazaki been brought on earlier, the score could have been very different. Had Japan been remotely near full strength, and not a collection of youngsters, then the score would certainly have been very different.

Ecuador, Chile's next opponents, will surely be looking at a chance of redemption on Friday after their 4-0 hammering by Uruguay. Chile have suffered with the physicality of the Ecuadorians in the past, and the quick wingers and centre-forward Enner Valencia are unlikely to be as forgiving as the young Japanese.

Chile players celebrate after scoring a goal against Japan in the Copa America. Getty Images

Rueda may be tempted to return to the idea of playing three centre-backs that he floated in the friendly against the United States back in March. It allows the team to throw Isla and left-back Jean Beausejour forward and still retain defensive cover. A former coach of the Ecuador national team, he will be aware that the second match will be much more difficult than the first.

While he is worrying, the sizeable contingent of Chilean travelling fans will be celebrating. They created a fiery atmosphere in Sao Paulo's Morumbi stadium - but the crowd of 23,000 was another disappointment for the competition. It had been hoped that the city's massive community of Japanese descendents might come out to support the country's national team. The fact that this did not happen is a cause for concern in a competition that is featuring too many empty seats.

Brazil is an expensive destination for other South Americans, and the response from the locals has not been good - tickets have been overpriced, the collection procedure is awkward and with domestic league games taking place up until the night before the big kickoff, there was insufficient time for a big marketing push.

The quality of some of the goals scored in the opening days deserves a bigger crowd. But crowd size will be the least of Rueda's worries as he tries to figure out how to guide this ageing batch of Chilean veterans out of a challenging group.