Egan, coming off a career-best season, hurt his left elbow midway through the second half of the Warriors' 16-12 loss in Auckland on Friday night.
Making his club debut, Capewell went down clutching his ribs after a hit from Sharks winger Ronaldo Mulitalo early in the second half.
A club representative told AAP on Saturday it may take until next week to know whether the pair would be available for the round-two clash with Melbourne.
Egan's arm was caught in an awkward position as he and a group of teammates attempted to drive Sharks centre Siosifa Talakai back into the in-goal.
A Warriors trainer strapped the hooker's elbow on the field and he appeared able to move his arm painlessly.
But Egan, who had only just returned from a spell on the bench, left the field for further medical assessment and did not return.
Warriors coach Andrew Webster described the injury as "awkward and scary" given the unusual circumstances that caused it and the level of pain Egan suffered initially.
"It's the way he landed when he came over the top (in the tackle), he planted his arm down there," Webster said.
"We'll just wait for scans. It could be fine, it might be nasty. We don't know yet."
Egan was replaced at dummy half by Freddy Lussick, who appears a natural choice to fill in for next Saturday's clash with the Storm at AAMI Park.
Dylan Walker substituted in for Capewell on the Warriors' right edge early in the second half but the premiership winner managed to return 10 minutes later and finish the game.
Webster believed Capewell had suffered rib cartilage damage and would need to be monitored.
"That can be worse than broken ribs sometimes, from what people have said," Webster said.
"He was tough enough to come back again and finish the game but I think he's going to be a sore boy tomorrow.
"We'll know more in the coming days."
Webster admitted the timing was less than ideal as the Warriors, preliminary finalists in 2023, looked to bounce back in round two.
"Those things just happen in rugby league don't they," he said of the injuries.
"If you're going to get a rib cartilage, you don't want it in round one because it lingers for four or five weeks. What's the chances tonight?
"It's just one of those nights."
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