The Pakistan Cricket Board said on Wednesday he had been sent for an MRI scan following the tourists' 360-run loss and that the team's medical panel would assess the result.
Shahzad took five wickets on his debut at Perth Stadium in a raw pace unit.
Pakistan are already depleted in attack, with injured quick Naseem Shah sidelined and Haris Rauf having opted out of the series to play in Australia's T20 Big Bash League.