Players have reported suffering vomiting, headaches and excessive weight loss since the sweltering A-League football clash between Perth Glory and Adelaide United.
The players association plans to investigate why its request to further delay Monday's match at Perth's NIB Stadium was not heeded.
The match was delayed by half an hour to 5.30pm but temperatures were still nudging 39 degrees at kick-off and 35 degrees when the match finished.
The Professional Footballers Australia chief executive Adam Vivian said the PFA was in contact with the players both before the game and afterwards, concerned for their welfare.
"Some players have since reported heat illnesses, including excessive weight loss, headaches and vomiting," said Vivian.
"The PFA will continue to monitor the players' health and will be conducting further discussions with Football Federation Australia and the clubs."
"We will be asking them to share with us the advice in which they were satisfied the players' health and safety was not compromised by proceeding with the match at that time."
He noted that Perth's next A-League fixture was scheduled to kick-off at 5pm on January 25, a time of year when temperatures in excess of 40 degrees Celsius have been recorded.