Coach Jill Ellis did not start midfielder Lindsey Horan against Spain, replacing her with Samantha Mewis. Horan had a yellow card in the team's second match. Players who accumulate two yellow cards through the quarterfinals must sit out the next game.
The winner of Monday's match faces France in the quarterfinals in Paris on Friday night.
Ertz, a defensive midfielder, started in the team's tournament-opening 13-0 victory over Thailand, falling back to the defensive line because center back Becky Sauerbrunn sat out with a minor injury. She started and scored her first World Cup goal in the team's 3-0 victory over Chile, but did not play in the team's 2-0 victory over Sweden because of the minor injury.
Sauerbrunn was at center back for the third straight game alongside Dahlkemper, with Kelley O'Hara on the right and Crystal Dunn on the left.
Rose Lavelle and Mewis rounded out the midfield with Ertz.
Spain, playing in its second World Cup but making its first appearance in the knockout round, had just three lineup lineup changes from its last match, a scoreless draw against China to conclude the group stage.
Seven of Spain's players have started each game in France, including Jennifer Hermoso, who went into the match against the United States with a team-leading two goals.