Serbia’s women’s volleyball team eliminated the world’s top-ranked team, the United States, on thursday in a shock upset after the undefeated Americans lost their top player to a knee injury.

Serbia, playing in their first Olympic semi-final, were riding high after sending Russia home two days earlier and defeated the United States 20-25 25-17 25-21 16-25 15-13.

The U.S. team won the first set but Serbia, driven on by their formidable spiker Brankica Mihajlovic, took control after America’s top-scoring middle blocker Foluke Akinradewo went off with a left knee injury sustained in the opening set.

The U.S. had beaten Serbia 3-1 in preliminary games and were favorites to take their first gold medal in women’s volleyball. They won the World Championship in 2014 and took silver in the last two Olympics where they lost both finals to the Brazilians, their traditional rivals who were beaten by China on Tuesday.

The Americans had the crowd in Rio’s rowdy Maracanazinho stadium rooting against them. Mainly Brazilian spectators booed the U.S. servers and cheered when the Serbian players scored, chanting “Ole ole ola, Serbia, Serbia.”