United States women's team forward Mallory Swanson has a torn left patella tendon, U.S. Soccer confirmed Sunday.
Swanson was carted off the field during the first half of the United States' 2-0 win over Ireland on Saturday with the apparent left knee injury, a blow to the national team ahead of this summer's Women's World Cup.
She returned Sunday to Chicago, where she plays professionally for the NWSL's Red Stars, for further evaluation.
U.S. Soccer did not provide a timeline for Swanson's injury. The 2023 Women's World Cup gets underway in July in New Zealand and Australia.
Head coach Vlatko Andonovski called up 18-year-old Alyssa Thompson to replace Swanson, 24, in the squad for their Tuesday friendly against Ireland in St. Louis.
Thompson, the first overall pick in the 2023 National Women's Soccer League draft, made her senior national team debut in October.
Tuesday will mark the Americans' final match before Andonovski is expected to name his 23-player squad for the World Cup.
Swanson, who went by Pugh before her marriage to Chicago Cubs shortstop Dansby Swanson, has seven goals in five matches in 2023 -- five more goals than anyone else on the team.
Swanson was the team's leading scorer this year with seven total goals and a six-game scoring streak, tied for fourth longest in team history.
She was hurt in the 40th minute of the game at Q2 Stadium in Austin, Texas, after contact with Ireland's Aoife Mannion. Swanson cried out in pain as her teammates signaled to the sideline for the training staff.
"The emotions run high, regardless of what kind of injury," coach Vlatko Andonovski told reporters after the game.
The U.S. won the game thanks to a first goal for her country for defender Emily Fox in the 37th minute and an 80th-minute penalty from midfielder Lindsey Horan.
The U.S. is the two-time defending World Cup champion.
Information from ESPN's Jeff Carlisle was used in this report.