Aboubacar Keita, Columbus Crew (MLS)
Mark McKenzie, Philadelphia Union (MLS)
Chris Richards, Bayern Munich (GER)
Sam Rogers, Tacoma Defiance (USL)
James Sands, NYCFC (MLS)
One position without a lot of depth is center back after Richards and McKenzie. Richards was sold to Bayern Munich in January after six months on loan from FC Dallas. McKenzie was a 2018 finalist for Rookie of the Year with the Union and was called into the senior national team's January camp. Injuries and appendicitis have kept him out of the lineup this season, though. Sands, who wasn't part of the qualifying roster, played all but two minutes of NYCFC's first nine games before being injured. Keita was being groomed as the backup but has yet to play for the Crew. In a pinch, Matthew Real, Chris Durkin and Araujo can be used in the middle.
Chris Gloster, Hannover 96 (GER)
Edwin Lara, Leon (MEX),
Matthew Real, Philadelphia Union (MLS)
Real captained the U-20s in the Concacaf final against Mexico after splitting time at left back with Gloster, who is the likely starter in Poland. Gloster began the season with Hannover 96's U-19s but was later promoted to the reserve team. Lara, who played for Mexico at the 2015 U-17 World Cup, will probably be the odd-man out. He debuted for Leon's first team in the Copa MX this winter but has otherwise been limited to games on its Sub-20 team.
Brenden Aaronson, Philadelphia Union (MLS)
Frankie Amaya, FC Cincinnati (MLS)
Isaac Angking, New England Revolution (MLS)
Christian Cappis, Hobro (DEN)
Edwin Cerrillo, FC Dallas (MLS)
Griffin Dorsey, Toronto FC (MLS)
Chris Durkin, D.C. United (MLS)
Omir Fernandez, NY Red Bulls (MLS)
Anthony Fontana, Philadelphia Union (MLS)
Richie Ledezma, PSV (NED)
Alex Mendez, Freiburg (GER)
Paxton Pomykal, FC Dallas (MLS)
Brandon Servania, FC Dallas (MLS)
Juan Pablo Torres, NYCFC (MLS)
This is quite a list. Mendez (8 goals, 4 assists) and Pomykal (3 goals, 5 assists) were the key players in qualifying though Pomykal was often used in the attack in Ramos' 4-3-3 formation. Amaya, Servania and Torres were also big contributors in midfield in qualifying but they aren't assured of making final squad. Angking, Dorsey and Fontana were all dropped from the U-20 qualifying when changes were made after the first round.
Ledezma would have started in Bradenton but was injured and unavailable for qualifying. Only recently has he started playing for PSV's O19 team, but he has played well, scoring his first goal on Saturday. Cerrillo and Aaronson have been automatic choices for their teams in their first MLS seasons. Cappis scored in both international friendlies the U.S. U-20s played in March. Fernandez is just starting to have an impact on the Red Bulls and could end up being a contender for MLS Rookie of the Year.
At the defensive midfield position, Servania was excellent in qualifying and prized by Ramos for his ability to link up with Mendez and Pomykal, but the Alabaman was beaten out by Cerrillo for a starting job at FC Dallas and has been playing for North Texas SC in the new USL League. The other option is Durkin, one of the MLS players unavailable for qualifying. He had a great January camp.
Jonathan Amon, FC Nordsjaelland (DEN)
Andrew Carleton, Atlanta United (MLS)
Konrad de la Fuente, Barcelona (ESP)
Uly Llanez, Wolfsburg (GER)
Nick Taitague, Schalke 04 (GER)
Tim Weah, Celtic (SCO)
Llanez had seven goals and three assists that averaged out to 2.38 goals and 1.36 assists per 90 minutes in qualifying. Ayo Akinola and Pomykal were the other starters on the wings in qualifying. Since then, 17-year-old Konrad has emerged as a likely starter after a strong season for Barcelona's Juvenil A, which reached the semifinals of the UEFA Youth League. Taitague would have been an automatic choice if he wasn't injured. Carleton, a star on the U.S. U-17s two years ago, has dropped down the depth chart as he has been unable to get regular action on Atlanta United's first team (just 64 minutes so far in 2019).
Ayo Akinola, Toronto FC (MLS)
Justin Rennicks, New England Revolution (MLS)
Josh Sargent, Werder Bremen (GER)
Sebastian Soto, Hannover 96 (GER)
Rennicks started ahead of Soto in the Concacaf final against Mexico but hasn't played for the Revs since being injured in the U-20 friendly against France in March. Soto started the season on Hannover 96's U-19s but has gone on to play three games for the first team in the Bundesliga. Akinola, who scored seven goals in qualifying, is a Ramos favorite.