D.C. United captain Steve Birnbaum has been diagnosed with a concussion after a head-to-head clash in Saturday's 2-0 loss to New York Red Bulls, general manager Dave Kasper said Monday.
The 26-year-old centre-back suffered the injury in the second minute of added time when he collided with Red Bulls defender Damien Perrinelle while vying for a long ball.
He was taken to a New Jersey hospital after the match and remained in the team hotel an extra day, where he stayed with a team staff member before traveling back to D.C. on Sunday.
Birnbaum must take part in in the league's standard concussion protocol before he's allowed to return to training.
"He's feeling better," Kasper told the Washington Post.
Birnbaum is in his fourth MLS season after being drafted from the University of California Berkley in 2014, and has played the full 90 minutes in each of D.C.'s six games this season.
A United States international, he has made 10 appearances for his country, contributing a goal.