The average age of the U.S. men's soccer team players who've come to Philadelphia this week is 22. Almost all those players have played just a handful of games for the senior national team, if they've made it at all.

That sends a clear message: It's time for the national team to have some new leaders.

"There's an open door with leadership, and it takes all forms," U.S. coach Dave Sarachan said as his team opened training camp ahead of next Monday's game against Bolivia in Chester.

"It doesn't discriminate: You can be young and a leader; you can be old and a leader; you can be a non-starter and a leader," Sarachan said. "It will be very interesting for us as a staff to see how that emerges through the week."

Who might emerge from this group? Start on the back line, where central defenders Cameron Carter-Vickers and Matt Miazga could be atop the depth chart for a while. In midfield, Weston McKennie's role as a central traffic cop makes him a natural fit, and Christian Pulisic is already a star.

On the front line, there's an opportunity for Julian Green to reassert himself. It's his first national team camp since November 2016. He's still only 22, but he's the only player on this squad who has played in a World Cup.

Green never broke through at Bayern Munich, moving to VfB Stuttgart in January 2017. Stuttgart then loaned him to second-division team Gruether Fürth last August. He settled there, playing 24 games and scoring three goals — including a pretty one in the season finale May 13.

"He finished on a good note with his club. … That's important when guys have been playing and also having some confidence," Sarachan said. "He's still got ability, [and] I felt he deserved a good look this week in this environment. … I think this is a good opportunity for him to jump in."

While Sarachan's roster has a lot of wingers who can play forward, there are only two pure strikers: 21-year-old Andrija Novakovich, who made his national team debut in March; and 18-year-old Josh Sargent, a star of recent youth national teams.

"They understand that they're competing for [a start], if we decide to play with one striker," Sarachan said. "That's still open for this week, depending on how we want to line up."

There are a few true veterans on the squad, including outside backs Jorge Villafaña and Eric Lichaj. Sarachan is looking to them to be teachers as much as players.

"These are guys that have perspective," Sarachan said. "That's a very important piece to the roster build: to have guys like them continually in their ear to remind them what this is about."

More U.S.-Bolivia coverage

Christian Pulisic has grown up since his last national team game in Philadelphia

Julian Green never gave up on returning to the U.S. national soccer team