Pulisic, 27, arrived at the team's training base wearing a protective sleeve on his left calf before briefly joining his team-mates for a pre-session huddle. He then left with medical staff and headed to the gym, where he trained individually rather than with the group.
The AC Milan forward suffered the injury against Paraguay in the United States' 4-1 opening win, where he assisted two goals and set up the performance before being substituted at the break.
"Taking a little bit of precaution today, but I'm hoping I'll be fine the next few days," Pulisic said after that match.
US officials have declined to offer a firm update on his status, and the continued absence from group training has become the defining talking point ahead of Friday's game at Lumen Field.
Australia have already beaten Turkey 2-0 in their opening fixture and arrive in Seattle as one of Group D's two unbeaten sides. For a US team carrying enormous co-host expectation, facing the Socceroos without their best attacking player represents a significant test of squad depth.
Tyler Adams, who has seen up close the pressure Pulisic carries as America's standard-bearer, spoke about the scale of his team-mate's burden.
"I can't even imagine the weight that's on his shoulders — from such a young age, he was the hope of American soccer," Adams said. "He's a star, not just for the US team but in world football."
Adams added that he believes Pulisic will be ready to face Australia despite the training concerns.
Head coach Mauricio Pochettino has other attacking options available, with Giovanni Reyna, Timothy Weah and Brenden Aaronson all capable of stepping in if required, but none carries the same combination of experience and end product Pulisic brings.