With the 2015-16 European campaigns kicking off, a number of American youngsters are heading into hugely important seasons with their club teams. Here's a quick look at 10 Euro-based prospects 22 years old or younger -- all but one of them eligible for the U.S. under-23 squad that will attempt to qualify for the 2016 Olympics this October -- with plenty to prove this season.
John Brooks | Age: 22 | Pos: Defender | Team: Hertha Berlin (Germany)
Like most young center backs, Brooks has found consistency difficult to come by during the early part of his career. He was outstanding for Hertha during the second half of the 2014-15 Bundesliga campaign, helping his hometown club avoid relegation, but he struggled at the beginning. He'd started 24 of 34 games when it was over, 10 more than the season before. This season, he'll look to be an ever-present contributor. Senior team coach Jurgen Klinsmann will be watching closely. So will U23 boss Andi Herzog, though there is no chance Brooks will skip the senior team's Oct. 10 Confederations Cup playoff against Mexico to play with the U23s, which could have the opportunity to clinch a spot in the Olympics the same day. But if Brooks proves that he's an indispensable part of Hertha's team, it won't bode well for Herzog's changes of getting him released for Rio de Janeiro next August, as the Summer Games will conflict with the start of the 2016-17 German season.
Cody Cropper | 22 | Goalkeeper | Milton Keynes Dons (England)
Cropper has been on the bench for Premier League games (with Southampton in 2013) and senior international matches with the U.S., but the Atlanta-born, Minnesota-raised backstop didn't make his first-team club debut until Tuesday, when he helped his second-tier club beat fourth-division Leyton Orient in the English League Cup. The win might allow Cropper to play in the next round. One way or another, he needs games ahead of CONCACAF's Olympic qualifying tournament in October. Cropper has plenty to prove. He's made several costly gaffes playing for the U.S. (with the U20s at the 2013 World Cup, and with the U23s at the Toulon Tournament a few months ago) and could face stiff competition from Zack Steffen -- who was stellar for the U.S. at the 2015 U-20 World Cup in June -- when qualifying kicks off.
Julian Green | 20 | Forward | Bayern Munich (Germany)
After a disastrous loan from Bayern to Hamburg last season resulted in just a handful of first-team appearances (none in the second half of the Bundesliga season), Green can't afford another lost season at a crucial time in his development. Yet by opting to stay at Bayern this season, Green has committed to playing with the German behemoth's U23 side, which competes in the country's fourth division. It's a questionable approach, especially with clubs in Europe and MLS reportedly interested in acquiring him on loan.
Of course, there is some value in training regularly with one of the best teams in the world, which Green will do this season. And it's always possible that with consistently stellar performances in practice and with Bayern's U23s, Green could work himself into coach Pep Guardiola's first-team rotation. You have to give the youngster credit for betting on himself. But trying to earn consistent first-team playing time in one of the most competitive squads in the world still seems like a low-percentage play from Green given the safer options available.
Emerson Hyndman | 19 | Midfielder | Fulham (England)
The technically gifted Texan turned heads at the U-20 World Cup, where he captained the U.S. during its run to the quarterfinals, and top-flight clubs around Europe took notice. Teams from the English Premier League, German Bundesliga, the Dutch Eredivisie and La Liga in Spain are all interested in Hyndman, according to reports. The midfielder seems committed to moving -- entering the final year of his contract with Fulham, he's opted not to sign an extension -- which puts him in an interesting situation. If it's determined Hyndman can't be retained, Fulham would almost certainly sell its former academy product before the end of the current transfer window, when his value will be highest. But it also means it might opt not to play him until then. Indeed Hyndman, who as an 18-year-old made nine starts for the Cottagers in the first half of 2014-15 before a broken collarbone he suffered playing for the U.S. in CONCACAF's U20 championship prematurely ended his season, was an unused substitute in the first two games of the new season.
Jerome Kiesewetter | 22 | Forward | Stuttgart (Germany)
The Berlin native made his Bundesliga debut last season and will be looking to build on his two first-team appearances after being named to Stuttgart's first-team roster for the upcoming campaign. If he's getting playing time early, he probably wouldn't be released for the first part of CONCACAF's Olympic qualifying tournament, though he could be available for the crucial knockout stage because it falls during FIFA's October fixture window. Before that, he'll likely join up with the U23s next month in England for friendlies against England and Qatar. Kiesewetter played against both teams at Toulon, where he also scored a well-taken goal against the Netherlands.
Shane O'Neill | 21 | Defender | Apollon Limassol (Cyprus)
In a transfer that few saw coming, MLS club Colorado Rapids sold its homegrown center back to the obscure Cypriot side. While his destination was surprising, the fact that O'Neill was moved wasn't. Though the Irish-born defender started 47 games for the Rapids in 2013 and '14, he had made just three under coach Pablo Mastroeni this season. The deal should allow him to play for the U.S. U23s next month, but he'll have to show well in order to crack Herzog's squad ahead of qualifying the following month.
Rubio Rubin | 19 | Forward | Utrecht (Netherlands)
Rubin made waves in 2014-15, his first full professional season, making 28 Eredivisie appearances (21 of them starts) -- an unprecedented number for a teenage American forward in Europe. This year he needs to score goals. The Oregon native managed just three in the league in 2014-15, and while it's hard to nitpick when Rubin can also set up teammates (he was also often deployed out wide), it wouldn't hurt the striker to be a little bit more selfish in front of goal. He did net two goals in four starts for the U.S. at the U-20 World Cup. Other Americans (Jozy Altidore, Michael Bradley, Aron Johannsson) have had success scoring in the defensively challenged Dutch league, and Rubin seems just as capable. Avoiding a sophomore slump will be important. But the Netherlands still seems like the perfect place for him to take the next step. A prolific season could even see him follow in the footsteps of Altidore and Johansson and graduate to a bigger league.
Bobby Wood | 22 | Forward | Union Berlin (Germany)
Expectations are high this season for Wood after the Hawaiian scored game-winning goals against global titans Netherlands and Germany four days apart in June. The strikes helped Wood move from 1860 Munich to fellow second-tier club Union Berlin, where he should get the regular playing time that has eluded him over the past few injury-plagued seasons. He's already started Union's first three games of the new campaign. He hasn't scored yet, but strikers can be streaky. And a hot foot could vault Wood -- who is a month too old to play for the U.S. U23s -- into the senior team's starting lineup if the American forwards not named Clint Dempsey continue to struggle.
DeAndre Yedlin | 22 | Defender/midfielder | Tottenham Hotspur (England)
Yedlin's future is in doubt after the 2014 World Cup veteran was left off Tottenham's roster for last weekend's Premier League opener against Manchester United. A loan before the transfer window closes at the end of the month seems like a forgone conclusion at this stage. As long as he'll play, the pedigree of the borrowing club hardly matters. The worst option would be staying buried in the reserves at Spurs, which could compromise the former Seattle Sounder's chances of being called up by Klinsmann for the Mexico match. If that happens, though, the club could agree to release Yedlin to the U23s for the entirely of the qualifying tournament -- a clear silver lining for the U.S.
Gedion Zelalem | 18 | Forward | Arsenal (England)
The highly touted Zelalem showed flashes of brilliance during the first round of the U-20 World Cup but faded noticeably as the competition wore on. The post-tourney consensus was that the slightly built playmaker isn't ready to play against grown men on a regular basis. It's no surprise then that Zelalem didn't make the Gunners' first-team roster ahead of the new season. Still, the Washington, D.C.-area product -- who remains eligible to compete at the next U20 World Cup in 2017 -- continues to show his ability at the youth level. Whether Herzog thinks that's enough to help the U.S. this fall remains to be seen.