COMMERCE CITY, Colo. >> Goalkeeper Tim Howard’s uniform was filled with grass stains after the first day of training camp.

And this was considered a light workout.

“Just getting everybody back together, getting a sweat,” Howard said Monday after the U.S. squad went through a roughly 60-minute workout. “Day by day, we’re just trying to add on to the pile, put some concepts in and get some understanding between players.”

What awaits the squad in resumption of the final round of World Cup qualifying is certainly a gantlet. They have a game against Trinidad and Tobago on June 8 in Commerce City and then at Mexico three days later.

There’s little margin for error, with the U.S. currently in fourth place in the six-team standings. They have three home and three away matches remaining. The top three teams qualify, with the fourth-place squad going to a playoff against Asia’s No. 5 nation.

“We need to keep climbing that table. We feel like this is a good opportunity to do it,” said Howard, now with the Colorado Rapids and who will feel right at home with the Trinidad game on his turf at Dick’s Sporting Goods Park. “One game, that’s as far as you can look. You can’t look to next week or the week after or two months from now.”

For now, Howard will be coach Bruce Arena’s goalkeeper over Brad Guzan, Ethan Horvath and Nick Rimando, who all were invited to camp. But it’s an ongoing evaluation.

“We have good goalkeepers here. That’s the least of my worries, to be honest,” Arena said.

Given the short amount of time between games, Arena fully plans on using more players than usual. One particular competition to watch will be at right back between Timmy Chandler and DeAndre Yedlin.

“I have a close eye on everything,” Arena said. “We have a bunch of good players here. … We’re watching everybody and thinking about how we can best utilize everyone.”

The roster features a solid blend of youth and experience. Leading the youngsters is Christian Pulisic, the 18-year-old Borussia Dortmund midfielder who last weekend became the youngest American to win a club medal in Europe.

On the veteran side are players such as Clint Dempsey, Jozy Altidore, DaMarcus Beasley, Michael Bradley and Howard, all of whom have more than 30 World Cup qualifying appearances.

“We’re past the experimentation phase. These are all guys who the manager believes in whole-heartedly,” Howard said. “They’re not here for anything other than to play minutes, play important minutes.”

Arena couldn’t agree more.

“This is a nice group we have here. Hopefully, we can find the right balance in the team, putting them in the right position to complement them both individually and collectively,” Arena said. “If we can accomplish that, there’s no reason to believe we can’t be successful in these two games.”

Joining the camp in Colorado are a few players who weren’t with the squad in March. Guzan, Chandler, Fabian Johnson, Bobby Wood, who grew up in Hawaii, and Yedlin are all on the field. Guzan didn’t participate because his wife was expecting their second child, while the others were dealing with injuries, illnesses and yellow-card suspension.

Now, it’s a matter of getting their timing down — and accustomed to the altitude.

“There’s no reason to make it an excuse,” midfielder Paul Arriola said. “Just doing the best we can to acclimate to it.”

Arena’s squad will get things rolling in a friendly against Venezuela in Sandy, Utah, on Saturday.

“That’s a good game for us,” Arena said. “It gives us a little bit of exercise at lower altitude, which isn’t perfect for what we need to do to get ready here and Mexico City, but it’s a start. Think it will be good to give a chance to 16 players and build from there — get us ready for Trinidad and Mexico.”