Putting together a roster for a national-team tournament is full of innumerable moving parts. There's the form and health of the players, as well as the willingness of clubs to have their performers take part. Timing is also an issue.

The CONCACAF Gold Cup would at first glance appear to be immune from the whims of club managers given that it is a confederation championship. But there are the rules, and then there is reality, which explains why U.S. men's national team manager Gregg Berhalter leaned heavily into his collection of domestic players in putting together his roster for the 2021 edition of the tournament.

There will be no Christian Pulisic, Weston McKennie or Tyler Adams, as they weren't even named to the provisional roster. Players need rest at some point, and there's also the desire to stay in the good graces of their clubs. The timing of the start of preseason in Europe also played a role. Berhalter highlighted the situation of Bryan Reynolds starting the year at AS Roma under a new manager in Jose Mourinho as one example, but there are others, including Greuther Furth midfielder Julian Green.

"We felt that it was more important for them to be in preseason with their team, and give them a good chance of making a positive impact with their new coaching staff or with their club, rather than to be in Gold Cup," Berhalter said during a Zoom call with reporters. "It was give-and-take, it was a juggling act, and it wasn't easy because we still want to put a team on the field that's going to compete to win the Gold Cup."

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So the focus on this tournament will be on giving playing time to select veterans like Nashville SC's Walker Zimmerman, Sebastian Lletget of the LA Galaxy and the Seattle Sounders' Cristian Roldan while also looking at some younger players who have shown well during the early parts of the MLS season.

"We think there's enough backbone in this group," he said. "We think there's enough veteran leadership in this group to make a run on winning Gold Cup."

In terms of the younger elements of the roster, there are more than a few compelling prospects. Sporting Kansas City midfielder Gianluca Busio has done plenty to impress in the early going, even as transfer rumors swirl around him. New York City FC defender James Sands and Portland Timbers midfielder Eryk Williamson are included as well. All three were omitted from the U23 roster that failed to qualify for the Tokyo Olympics.

In terms of explaining the big jump of Sands and Williamson, Berhalter explained that health was a factor. Sands struggled with injury toward the latter stages of last season, otherwise he would have been included in both the December and January camps. Berhalter added that a high ankle sprain sustained during the January camp hampered Williamson's progress. Both players have since recovered and are back to their best.

As for Busio? "It's about form, and his time has come," said Berhalter.

For the New York Red Bulls' Caden Clark, his time will have to come later after undergoing an appendectomy.

"He was a guy who I was really looking forward to working with," Berhalter said. "[He's] a really good player, [with] really good spatial awareness, really good balance with turning between the lines, really good vision from final pass and ability score a goal. It's really unfortunate how things work out sometimes, but we know that this kid has a bright future, and we're going to continue to monitor him when he goes to Leipzig."

Given all of these considerations, there are some vulnerabilities in the roster. Berhalter admitted that the team was "thin" at center-back once you get past Zimmerman and Atlanta United's Miles Robinson. It will be up to Sands and D.C. United's Donovan Pines to step in and provide depth.

The winger positions are another area that have some question marks, with Berhalter noting that "I don't think we have true wingers in this group." D.C. United's Paul Arriola and the Colorado Rapids' Jonathan Lewis are the closest fits, but Berhalter expects Schalke 04's Matthew Hoppe and SC Caen's Nicholas Gioacchini -- both strikers by trade -- to get some minutes out wide.

One player who isn't on the roster is LA Galaxy right-back Julian Araujo. Araujo holds dual citizenship with Mexico, and Berhalter said that the defender was "not ready to fully commit to the team." Had Araujo played in the Gold Cup, he would have been cap tied to the U.S., and with the U.S. team enjoying something of a logjam at right-back with Sergino Dest, Reggie Cannon and veteran DeAndre Yedlin, it would seem that Araujo is keeping his options open. But Berhalter made it clear he rates the Galaxy defender highly.

"We think [Araujo is] an outstanding player, and we think he can make a run at being a starter on this team," he said. "A lot of it's going to be up to his form and his development, but he's a young, talented player, and we think that he does have a future with this team."

Now the challenge is to progress far into the tournament with the players available and prepare for the bigger battles ahead.

"We get to work on another group," Berhalter said. "We get to solidify this pool so that when we go into qualifying, we know where everyone stands."