Midfielder Gedion Zelalem, an Arsenal prospect from the Washington area, will undergo surgery soon for a knee injury suffered while playing for the United States at the Under-20 World Cup in South Korea, his family told the Insider on Wednesday.

He will need at least six months to recover from the ligament damage.

The U.S. Soccer Federation announced earlier Wednesday that Zelalem, 20, would miss the remainder of the tournament but did not disclose any details. In the statement, the Federation said Zelalem would consult with the U.S. and Arsenal medical staffs in determining a course of action.

Arsenal, which is preparing for Saturday’s FA Cup final against Chelsea, has yet to comment on the injury.

“For Gedion, this was his second U-20 World Cup, so his experience was invaluable for us,” U.S. Coach Tab Ramos said in a prepared statement. “His passing ability is second to none in this tournament, and we’ll miss that. He was running the team from his position.”

Zelalem, a central midfielder, came off in the 34th minute of a 3-3 draw with Ecuador on Monday, the Americans’ opening group match.

Zelalem was born in Germany and came to the United States with his family in 2006. He became a naturalized citizen in late 2014. His soccer skills were honed with the Olney Rangers youth team and he played one season at Walter Johnson High School in Bethesda, Md. Midway through his sophomore year, he moved to London to join Arsenal’s youth system.

After making an impression on longtime Gunners boss Arsene Wenger, Zelalem seemed to have a bright future with the first team. However, as a teenager, he was not able to find a place in the elite squad and went on loan to Scottish side Rangers last season (21 matches, 15 starts) and VVV Venlo, the Dutch second-flight leader, for the second half of this season. He appeared in nine league matches, with one start and one goal.

It’s unclear what plans Arsenal had for him next season. The injury, however, will keep him off the field until mid-winter, if not longer.