Star forward Alex Morgan left the game after turning her left ankle in the 37th minute, a blow to the United States in its 5-0 win over Guatemala in the CONCACAF Women's Championship on Friday night.
Morgan, who has 49 goals in 77 international appearances, first hurt the ankle during training late last October, then played against Brazil on Nov. 10. She was sidelined until returning to action with her club, the Portland Thorns, on June 7.
Morgan was to have a scan to determine the extent of the injury.
Tobin Heath scored twice, and Carli Lloyd, Whitney Engen and Megan Rapinoe had one goal each as the U.S. improved to 2-0 in the group stage of tournament, which serves as qualifying for next year's World Cup. Goalkeeper Hope Solo got her 75th shutout and didn't need to make a single save as the Americans outshot Guatemala 21-0.
Heath scored the first goal from 4 yards with a sliding right-footed shot in the seventh minute off short a pass from Sydney Leroux, beating goalkeeper Alicia Navas.
Lloyd doubled the lead in the 46th off an assist from Leroux, and Heath made it 3-0 in the 57. Engen scored in the 58th and Rapinoe in the 66th.
Seeking its third World Cup title but first since 1999, the U.S. leads Group A with six points, followed by Haiti, and Trinidad and Tobago (both 1-1) with three each. Guatemala (0-2) is last.
The top two teams in each of two groups advance to the semifinals Oct. 24 in Chester, Pennsylvania. The top three teams qualify for the World Cup in Canada, and the loser of the third-place game meets a South American nation in a playoff for another berth.