Chile manager Rueda has been the star of the 2019 Copa America

Who has been the star of the Copa America so far?

Going into the Copa America semifinals, it is hard to think of a truly outstanding player, one who has imposed his quality on the tournament. There is still time, of course, for one to emerge -- and what happens from now on in will weigh heavier than anything that has taken place up to this point.

So far, though, it is difficult to think of anyone who has had a better tournament than Reinaldo Rueda, the Colombian-born coach of Chile.

He took on the impossible job, inheriting a team for which the only way seemed to be down. Chile had waited 99 years to get their hands on the Copa America trophy. They finally won it in 2015 and retained their title in the special Copa America Centenario the following year.

But then came the problems. An ageing squad ran out of steam and failed to qualify for last year's World Cup. They were burned out; four consecutive years of international tournaments (those Copa flanked by the 2014 World Cup and the 2017 Confederations Cup) had taken their toll. The players were in physical decline, and, under the pressure of disappointing results, long running spats in a difficult dressing room were opening up into serious fissures.

Then in stepped Rueda.

There was logic behind his choice. Winning the Copa Libertadores in 2016 with Colombia's Atletico Nacional imposes a certain respect and he has World Cup experience, having previously taken both Honduras and Ecuador to the competition. He also had made his name as a youth development specialist, taking his native Colombia to third place in the 2003 World Under-20 Cup. Rueda, then, seemed to tick all the boxes. He was the man to renew the side.

- Copa America: All you need to know
- Full Copa America fixtures schedule

But how to rebuild without the raw materials? Domestic Chilean football is in a poor state, as Chile are only country in South America who have already had all of its participants eliminated from both the Copa Libertadores and Copa Sudamericana. There is a dearth of young talent and there has been an excess of pressure.

The Chilean press and public have been spoiled by recent success. They have expected the team to rebuild and keep winning -- an all but impossible demand, while Rueda has been attempting to construct a fresh side under pressure to achieve results. After every friendly defeat there have been calls for his dismissal. Rueda has been forced to rely on the old guard and throughout the Copa America, many of Chile's large travelling army have even booed his name when his lineups are announced ahead of kick-off.

But in his quiet, methodical way, Rueda is carrying out a first-class job.

He dealt with the dressing room problem by leaving out the veteran captain and goalkeeper Claudio Bravo, whose relationship with Arturo Vidal appeared to have broken down. In has come the naturalised Argentine Gabriel Arias -- a steady and undoubted success, albeit one who has little ability on the ball. The loss of Bravo deprives Chile of one of their key features of the last decade -- a keeper who can operate as an auxiliary midfielder, taking responsibility 40 metres from goal and building moves from the back.

This is not quite so important because Chile no longer defend high. Their ageing limbs will not permit a repeat of their high intensity pressing game, so now they have to cover up more, and defend closer to their own goal. This makes defensive height a necessity -- and so in has come Guillermo Maripan, a tall, throwback centre-back.

There has also been another key change in front of the back four. Marcelo Diaz was the brains of the old Chile side, organising the moves from deep. That said, he had become increasingly vulnerable defensively, and so he has given way to Erick Pulgar -- tall, combative midfielder with a capacity to pass over range. Rather than the quick, intricate moves through the centre orchestrated by Diaz, Chile now sit deeper and look to spring Alexis Sanchez in space down the flanks.

Rueda, then, has worked away steadily at adapting Chile's playing style to the ageing resources at his disposal. Eight of his starting 11 have passed the 30 mark -- and Eduardo Vargas is only a few months shy of making it nine.

They cannot be the same side that swept Mexico aside 7-0 in the 2016 Copa, swarming all over their opponents from start to finish. They must now dose their efforts, because in the eternal battle between the athlete and the march of time, there is only one winner.

But the athlete's eventual defeat can be delayed by two things. One is excellent physical preparation -- and Rueda works with highly-rated specialist Carlos Eduardo Velasco, who will seek to ensure that the team have enough gas in the tank to take them through to the end of the tournament. The other vital component is mental cunning.

Perhaps the best example is boxer Muhammad Ali. Once the marriage of speed and power, after his enforced mid-career layoff he had lost some of the former. This forced him to adapt, which he did, becoming famous for his "rope-a-dope" style, where he let his opponent wear himself out before choosing the right moment to take the initiative. Guiding him in the corner was the legendary Angelo Dundee.

Reinaldo Rueda is the Angelo Dundee to the likes of Arturo Vidal and Alexis Sanchez, who will hope to float and sting their way past Peru and into a third consecutive Copa America final.