Greg Garza (foreground) departed training camp in Chula Vista, California, after being diagnosed with a low-grade quadriceps strain.
The 27-year-old defender started on Atlanta United's 2018 MLS Cup championship team but was traded to FC Cincinnati in the offseason. He will return to Cincinnati for treatment.
Garza (10 caps) will not be replaced on the U.S. camp roster, which now stands at 27 players and includes two uncapped players as options at left back. Montreal Impact defender Daniel Lovitz should be first in line to step in at left back at the camp, but San Jose's Nick Lima has played both outside back positions. They are 27 and 24, respectively.
Six other players got starts at left back in 2018. Antonee Robinson led with four starts but struggled defensively and hasn't played for Wigan Athletic since undergoing ankle surgery in November.
U.S. left back: 2018 starters
4 Antonee Robinson (Bolivia, France, Brazil, Colombia)
3 Jorge Villafana (Paraguay, Ireland, England)
1 Justin Morrow (Bosnia & Herzegovina)
1 Eric Lichaj (Mexico)
1 Ben Sweat (Peru)
1 Shaq Moore (Italy)
There are several promising players coming down the pipeline, but they are all teenagers. Chris Gloster, 18, has already promoted from Hannover 96's U-19s to its second team in his first season in Germany. Matt Real, 19, captained the U-20s through much of the 2018 Concacaf championship and is expected to get first crack at starting for the Philadelphia Union on the backline with Auston Trusty and Mark McKenzie, who are both in the national team camp.
Edwin Lara, 19, has returned to the U.S. youth program after playing for Mexico at the 2015 Under-17 World Cup. Perhaps the best left back prospect is the youngest. George Bello (photo) turns 17 on Tuesday. He made three appearances last season for Atlanta United and scored one goal. His emergence was one reason Atlanta United traded Garza to FC Cincinnati.
GOALKEEPERS (4): Alex Bono (Toronto FC; 1/0), Sean Johnson (New York City FC; 5/0), Tyler Miller (LAFC; 0/0), Zack Steffen (Columbus Crew; 6/0)
DEFENDERS (9): Reggie Cannon (FC Dallas; 2/0), Justen Glad (Real Salt Lake; 0/0), Nick Lima (San Jose Earthquakes; 0/0), Aaron Long (NY Red Bulls; 2/0), Daniel Lovitz (Montreal Impact; 0/0), Mark McKenzie (Philadelphia Union; 0/0), Keegan Rosenberry (Colorado Rapids; 0/0), Auston Trusty (Philadelphia Union; 0/0), Walker Zimmerman (LAFC; 4/1)
MIDFIELDERS (11): Kellyn Acosta (Colorado Rapids; 23/2), Paul Arriola (D.C. United; 17/2), Corey Baird (Real Salt Lake; 0/0), Michael Bradley (Toronto FC; 142/17), Russell Canouse (D.C. United; 0/0), Marky Delgado (Toronto FC; 6/0), Jonathan Lewis (New York City FC; 0/0), Sebastian Lletget (LA Galaxy; 5/1), Djordje Mihailovic (Chicago Fire; 0/0), Cristian Roldan (Seattle Sounders; 5/0), Wil Trapp (Columbus Crew; 11/0)
FORWARDS (3): Jeremy Ebobisse (Portland Timbers, 0/0), Christian Ramirez (LAFC; 0/0), Gyasi Zardes (Columbus Crew; 40/6)
In parentheses are caps and goals.