NEW YORK (AP) — Ryan McIntosh, the ballperson who lost his leg when he stepped on a land mine in Afghanistan, was working the men’s semifinal Sunday between Novak Djokovic and David Ferrer at the U.S. Open.

McIntosh, 23, is an Army specialist. He was walking with his platoon through a river valley near Kandahar in December 2010 when he stepped on a pressure-plate land mine. He now wears a prosthetic right leg.

He learned about the chance to become a U.S. Open ballperson while competing this year at the Warrior Games, an Olympic-style sports festival for wounded soldiers.

McIntosh got good reviews early in the tournament from his supervisor and was rewarded with one of the plum assignments — a key match in Arthur Ashe Stadium on the final weekend.