Brazil have chalked up six wins since the World Cup without conceding a goal. But they are aware that they have not been playing well and are struggling to find a blend. The pressure is on them to win the Copa America, which gives added interest to their matches against Panama and the Czech Republic.

Questions abound. Can they find a way to use the talents of Roberto Firmino at centre-forward? Would he be helped by the capacity of Richarlison to provide some penalty-area presence? Might Lucas Paqueta establish himself as the most attacking member of the midfield trio? Would this free Philippe Coutinho to return to the attacking trio, where he is surely most comfortable?

Over the next few days, three teams are playing their first games with a new coach. Bolivia get the reign of Eduardo Villegas underway with a trip to face South Korea and Japan. But in this case, the coach is no stranger. Villegas was in charge for one game on a caretaker basis a decade ago. He is a successful figure in domestic Bolivian football, which provides most of the players in his squad. Villegas, then, is moving into familiar territory.

The same does not apply for Colombia, who are also in East Asia, playing the same opponents in a different order. Their new coach is Carlos Queiroz, a Portuguese coach with an impressive and varied CV, including spells in charge of Real Madrid and national teams all over the globe and two spells at Manchester United as an assistant to Sir Alex Ferguson. But Queiroz has never worked in South America. He is sailing into uncharted waters.

Somewhere in the middle is Eduardo Berizzo, the Argentine who has just taken over the national team of Paraguay. This country is new ground for him. But he has experience in South American World Cup qualifiers, both as a player for Argentina and as Chile assistant coach during the time of Marcelo Bielsa. His baptism comes against Peru, followed by Mexico.

Then there is the case of Argentina, who remain under the command of Lionel Scaloni. For the first time since the World Cup, Lionel Messi is back -- for Saturday's meeting with Venezuela in Madrid if not for the visit to Morocco on Tuesday. What is not clear is the structure into which Messi will fit. Scaloni's time in charge began soon after Argentina's disastrous World Cup, and for a caretaker with little experience, he made some bold noises. He talked of changing the style of the national team, of introducing a more direct manner of play. But this would not appear to be speaking Messi's footballing language. Will Messi go along with the new idea, or will his comeback force a return to a more possession-based style of play?

The game against Venezuela should be an interesting test because Argentina are facing an opponent who seriously believe they will make their World Cup debut in 2022. Venezuela have made steady progress and have now incorporated the best from the generation that reached the final of the 2017 Under-20 World Cup. They are one of the few sides that will not be underprepared for the Copa America in Brazil.

Ecuador, meanwhile, are still in the early days of the second spell in charge of coach Hernan Dario Gomez. It was Gomez who took them to their first World Cup in 2002. Back then, he made no secret of the fact that he did not take the Copa Americas of 2001 and 2004 particularly seriously, and it appears that he is taking 2019 in similar fashion. At the moment, he is happy to experiment. Main goal scorer Enner Valencia has withdrawn from the squad that will face the United States and Honduras. This leaves Gomez with one genuine centre-forward, 18-year-old Leonardo Campana, who was on impressive form in the recent continental U20 championships but has very little experience of senior football. Ecuador, then, seem content to be at the experimental stage.

Chile, under Reinaldo Rueda, are further down the line. Rueda has had a year in charge. Over the course of four wins, three draws and three defeats, there have been moments when the new coach has come under pressure. His task, to gently replace Chile's golden generation, always looked difficult, and he trusts that the coming games against Mexico and the U.S. will set him up for a good Copa America. His job could be at risk if things go badly in Brazil.

That leaves three teams who gave a reasonable account of themselves at the World Cup in Russia. On their return to the tournament after a 36-year absence, Peru and their young side were never disgraced. Results since Russia have been patchy, and the moment of truth is perhaps emerging for the current crop of players, who warm up for the Copa against Paraguay and El Salvador.

Uruguay head for friendlies in China on the back of four consecutive defeats. This, though, is a minor problem. The long-term headache is the inevitable truth that the strike duo of Luis Suarez and Edinson Cavani cannot go on forever. Both will be in their mid-30s by the time the next World Cup comes around and run the risk of being past their best. It is probably a blessing, then, that both have withdrawn injured from the trip to China, where Uruguay will face Uzbekistan followed by either Thailand or the hosts. The absence of the big two gives Maxi Gomez a chance to prove himself the long-term solution at centre-forward.

While some coaches might be happy to go to the Copa America in an unprepared state, learn some lessons and use them to prepare for next year's World Cup qualifiers, Brazil coach Tite cannot afford the luxury of such long-term thinking. The opposition might be undercooked, but the hosts need to get the recipe just right.