United States women's soccer star Mallory Swanson will almost certainly miss this summer's World Cup after suffering a serious knee injury during Saturday's friendly victory over Ireland.

US Soccer said in a statement on Sunday that Swanson, one of the stars of the US team, had torn a patella tendon in her left knee during Saturday's friendly in Austin.

Swanson was stretchered off the field in distress near the end of the first half after crumpling to the turf following a heavy challenge from Ireland's Aoife Mannion.

"Swanson suffered a torn patella tendon in her left knee," US Soccer said in a statement on Sunday. "She returned to Chicago today for further evaluation."

Swanson has been replaced by Alyssa Thompson in the US squad for Tuesday's return fixture with the Irish women in St.Louis.

No timeline for Swanson's recovery was given, but a torn patella tendon can often take at least six months to recover from.

The United States launch the defence of their World Cup crown against Vietnam in Auckland on July 21.

Swanson, who turns 25 later this month, is one of the stars of the US national team and has been in blistering form this year with seven international goals in five appearances.

The Chicago Red Stars striker also scored seven international goals in 2022.