Thompson will go for scans after returning to Sydney from New Zealand on Monday and is set to join Matt Burton (hamstring) in racing the clock to play the season opener against St George Illawarra on March 1.
The Dragons have their own injury concern out of All Stars camp, with prop Josh Kerr rolling his ankle at training and unable to line up for the Indigenous side.
The Bulldogs are due to fly out to the US on Thursday to participate in the NRL's third annual round-one showcase at Allegiant Stadium.
Bulldogs general manager of football Phil Gould said there was "concern" over the injury to Thompson, who had been set to start at prop for the Maori All Stars against their Indigenous counterparts on Sunday.
"He has "general tightness" in his calf muscle," Gould wrote on X.
"He didn't appear to experience an incident or acute injury … But players can tell be terrible at diagnosing their own symptoms … I have far greater confidence in the X-ray.
"When asked if he could've played if it was a grand final, he said he probably couldn't … That's a concern."
Thompson arrived from Newcastle this off-season as a major piece in the Dogs' premiership puzzle following the club's top-four finish last year.
In Thompson, Canterbury have the kind of physical middle-forward enforcer that has largely been absent from their rebuild under Cameron Ciraldo.
He would loom as a significant omission from the team in Vegas, with Ciraldo impressed by the big Kiwi in his first Bulldogs pre-season.
"He brings a physical presence, his character is something that you want in your forward pack," Ciraldo told reporters on Saturday night, before news of Thompson's injury.
"We're really grateful that he joined our club."
Thompson's injury came a day after Matt Burton left the pre-season defeat of Newcastle with an injury to his left hamstring.
Burton was walking unencumbered immediately after the 28-0 thrashing of the Knights on Saturday night, but will nevertheless go for scans.
"He said it's not too bad, it feels all right," Ciraldo said.
"If he's right to play, he'll play in Vegas. If not, I think (replacement halfback) Sean O'Sullivan did a great job today. It's pretty black and white."
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