The U.S. may face Australia in the World Cup without star Christian Pulisic

Players of the United States celebrate during their opening World Cup match, a 4-1 victory over Paraguay. The U.S. has an important match Friday against Australia. Dean Mouhtaropoulos/Getty Images hide caption toggle caption Dean Mouhtaropoulos/Getty Images SEATTLE — The performance of the U.S. men's national soccer team in Friday's match against Australia could come down to the health of star Christian Pulisic — and specifically, his left calf. The group stage game against Australia , set for 3 p.m. Eastern time at Lumen Field in Seattle, will be pivotal in determining the U.S.'s knockout-stage seeding. Both the U.S. and Australia won their openers — the U.S. over Paraguay 4-1 and Australia over Turkey 2-0 — meaning the winner of Friday's game between the two teams will be in the driver's seat to win the group. But a Pulisic absence on the left side could spell trouble for the Americans. After being kicked in the left calf by a Paraguayan player, Pulisic exited last Friday's game at halftime. The difference in the U.S. performance between the first and second half, after Pulisic was replaced by midfielder Sebastian Berhalter, was noticeable. Paraguay scored its only goal after halftime. "Christian is a really important player for us. He can be really dangerous on the wing side," said teammate and midfielder Sergiño Dest. Pulisic has been training individually all week long. On Thursday, U.S. …