Gedion Zelalem, a midfielder for the U.S. Men’s National Team and an Arsenal prospect, will miss the rest of the the Under-20 World Cup with a knee injury, U.S. Soccer announced Wednesday.

USMNT star Gedio Zelalem to miss rest of U-20 World Cup with Knee Injury

The 20-year-old German-born American tore his left ACL in the first half of Monday’s 3-3 tie against Ecuador, the USMNT’s opening group game in the South Korea tournament. Zelalem walked off in the 34th minute.

“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 statement. “His passing ability is second to none in this tournament, and we’ll miss that. He was running the team from his position.”

The midfielder is expected to undergo surgery and miss six months or more, according to the Washington Post. 

Zelalem, who plays for Arsenal’s Under-20 squad, has been on loan to Dutch second division team VVV Venlo. The central midfielder came to the United States with his family from Germany in 2006, and became an American citizen in 2014. After playing one year of high school soccer in Bethesda, Maryland, Zelalem moved to London halfway through his sophomore year to join Arsenal’s youth club.

The U.S. U-20 men next play Senegal on Thursday. Senegal leads Group F after defeating Saudi Arabia 2-0.

The final of the U-20 World Cup will be held on June 11.

Arsenal, which is set to play Chelsea in the FA Cup final on Saturday, has not yet commented on Zelalem’s injury.

WELLINGTON, NEW ZEALAND – JUNE 10: Gedion Zelalem of USA beats the challenge of Andres Tello of Colombia during the FIFA U-20 World Cup New Zealand 2015 Round of 16 match between USA and Colombia at Wellington Regional Stadium on June 10, 2015 in Wellington, New Zealand. (Photo by Hagen Hopkins/Getty Images)