GLENDALE, Ariz. – For two-and-a-half years, Jurgen Klinsmann tinkered. He experimented, demanding urgency as he steadily expanded the player pool. The German even dropped the USMNT’s most decorated player to prove a point.

Now, 24 hours before the US national team takes on Mexico on Wednesday (11 pm ET, ESPN and UniMas) in its last friendly before the final camp before the 2014 World Cup in Brazil, Klinsmann is tasked with trimming rather than expanding the group at his disposal.

Come May, the World Cup dream will remain intact for, at most, the 30 players named to the preliminary roster, which must be turned in to FIFA by May 13. The pressing question in Arizona is whether Wednesday night's game can actually advance or detract from anyone’s cause.

“This is a huge opportunity, and it has a bit of a weight,” Klinsmann told reporters during his press conference on Tuesday. “Now does it decide about who goes into camp or not? No. We aren’t deciding on one game who goes into camp six weeks from now.

"We’re going to review the last two-and-a-half years. We will talk through every player individually and put the puzzle together the best way possible.”

For now, he’ll put the 20 players in camp, only one of which hails from outside MLS, under the microscope against El Tri before using May’s pre-World Cup friendlies to handpick the 23 will board the plane to São Paulo.

Some – like Clint Dempsey and Michael Bradley – have little to fret about, their spots all but assured. Most, meanwhile, understand there’s still an element of uncertainty in play – no matter what their résumé says.

“The reality is in the last few years this team has had a lot of turnover,” forward Landon Donovan said. “Jurgen has made it very clear that if you’re not playing and performing, you can be on the chopping block just like anyone else. We’ve had that mentality from Day 1. We’ve all had moments where we haven’t played well and suffered for it.

“We understand very clearly that if you don’t perform well, you’re not going to be a part of the team that goes to Brazil. That’s the same for me just like anyone else. We keep that in our minds at all time.”

They’ll keep it there until June 2, the date final rosters are due to FIFA. Klinsmann said on Tuesday that he’d likely take the maximum in both numbers (the 30 players eligible to named to the preliminary roster) and time to make his final decision.

“Jurgen will be watching right up to that last minute,” Bradley said.

In the meantime, everyone from Donovan to new arrival Julian Green will do everything in their power with both club and country to force their way into the squad as the stakes reach their zenith.

“We don’t talk about it between the guys, but everybody knows it,” defender Michael Parkhurst said. “The opportunities are dwindling. This is it. This is the time you have to play well in order to be on that plane to Brazil. I think everybody understands that, but at the same time, we try and keep it light because we have to go out there and play free and play confident if you want to show well.

“A lot can change between now and six weeks from now,” he added.