Alex Morgan was subbed out with an injury and fans are worried

Despite the team's victory, one dark cloud looms: What exactly happened to the US's star striker, Alex Morgan?

Morgan was subbed out halfway through game after she suffered a hard foul and took a minute to get to her feet.

The player seemed to have some trouble recovering from the knock, though she finished out the first half. At the start of the second half, Carli Lloyd replaced her on the field.

Morgan has not yet addressed the injury publicly, and Coach Jill Ellis has only said that substituting her star striker was a matter of being "smart about things."

It's unclear if the injury is related to Morgan's knee surgery after the World Cup in 2015.

According to a 2015 USWNT press release, the player had "arthroscopic surgery on her right knee... to remove a plica, which is a small fold in the lining of the knee joint, that was causing her irritation."

Although Morgan played in all seven games for the US in 2015, the injury had caused some issues, the statement said.

With Morgan's future in this year's World Cup potentially in jeopardy, fans are a bit worried.

After all, the Olympic gold medalist striker scored a stunning five goals in the group stage against Thailand. Without her, the US could face some difficulty down the line at the World Cup.