SAN SALVADOR, El Salvador — U.S. star Christian Pulisic and goalkeeper Zack Steffen will miss the Americans’ opening World Cup qualifier at El Salvador on Thursday night.

Pulisic, the top American player, is regaining fitness after testing positive for COVID-19. He has said he is fully vaccinated.

U.S. coach Gregg Berhalter said it is too early to determine whether Pulisic will be available for Sunday’s match against Canada in Nashville.

Steffen has back spasms. Berhalter said Matt Turner will start against El Salvador.

» READ MORE: Soccer on TV: The United States men enter World Cup qualifying this week

The U.S. team announced shortly after its charter flight left Nashville International Airport that Pulisic did not make the trip.

The 22-year-old attacker missed Chelsea’s 2-0 win at Arsenal on Aug. 22 and a 1-1 draw at Liverpool on Saturday. He resumed training with the U.S. on Monday.

Brenden Aaronson or Konrad de la Fuente are the most likely replacements for Pulisic in the U.S. starting lineup.

The start of World Cup qualifying was delayed for a year due to the coronavirus pandemic. Because of the delay, the U.S. is playing three qualifiers in a FIFA window designed for two.

After the Americans host Canada, they play at Honduras on Sept. 8.

Pulisic is the first American to play in and win a European Champions League final, helping Chelsea win the title last season.

Steffen is the backup to Ederson at Manchester City.

» READ MORE: The U.S. roster for this month's World Cup qualifiers