The real business of preparing for the Copa America Centenario begins on Wednesday for the United States men’s national team, when taking on Ecuador at Toyota Stadium in Frisco, Texas. While Jurgen Klinsmann’s side beat minnows Puerto Rico 3-1 on Sunday, the encounter with fellow Copa America participants Ecuador will be the first time that he has his full 23-man squad for the tournament available.

And with just one more friendly left, against Bolivia on Saturday, before kicking off the tournament against Colombia on June 3, there remains plenty for the U.S. to address and little time for players to state their case for inclusion in the starting lineup.

“Having two opportunities to play friendlies against Ecuador and Bolivia means a lot to us, because it will give us hopefully a lot of good information of where our players are at, but also the terms of different styles they play down in South America,” Klinsmann said in a press conference ahead of the game. “So hopefully it teaches us a lot before we hit it with Colombia.”

One of the big questions to answer over the coming days surrounds the forward line, where Jozy Altidore’s absence through injury has again necessitated a rethink for Klinsmann. Clint Dempsey, now 33 years old, remains a mainstay of the team, but it is unclear whether the Seattle Sounders star will act as a lone forward, as he did following Altidore’s injury at the 2014 World Cup, or if he will be granted a partner. Currently leading the race to fill that role is Bobby Wood, fresh from scoring 17 goals in Germany’s second tier and earning a transfer to Bundesliga side Hamburg.

Perhaps even greater uncertainty surrounds the backline. Geoff Cameron would appear the first-choice center-back, but has been ruled out of the game with Ecuador due to a hamstring injury picked up on the final day of the Premier League season. His likely partner, John Brooks, meanwhile, could do with a positive showing having been inconsistent in his time with the U.S. and particularly struggling at last year’s Gold Cup.

As for Wednesday, with Omar Gonzalez a notable exclusion from the squad, Matt Besler looks likely to get the nod over Steve Birnbaum and Michael Orozco alongside Brooks. At outside back, Klinsmann has confirmed he still sees Fabian Johnson as a left-back, despite him having an impressive season in midfield for Borussia Monchengladbach. Johnson, though, is a fitness doubt for the match with Ecuador, as is right-back Timmy Chandler, who only joined the squad Tuesday after being forced off with injury in Eintracht Frankfurt’s relegation playoff on Monday.

It promises to be a tough assignment for Klinsmann’s outfit on Wednesday. Ecuador currently sits level on points at the top of South America’s World Cup qualifying table after winning its first four matches, before recording a draw and a defeat in its two games in March.

Despite the priority of getting to Russia in 2018, Ecuador coach Gustavo Quinteros has chosen a strong squad for the Copa America. Of the country’s leading players, only leading striker Felipe Caicedo has withdrawn because of injury. Still, Manchester United’s Antonio Valencia may also miss out on the starting lineup on Wednesday having joined the squad late following his participation in Saturday’s FA Cup final.

Fellow Premier League performers, Jefferson Montero of Swansea City and West Ham’s Enner Valencia, look set to be involved, while FC Dallas midfielder Carlos Gruezo could line up at his home stadium.

Start time: 8 p.m. EDT

TV channel: ESPN2, UniMás Univision Deportes

Live stream: Watch ESPN,