Professional Footballers Australia plans to investigate why its request to further delay Monday's match at Perth's nib Stadium was not heeded by FFA.

The match was delayed by half an hour to 5.30pm, with drinks breaks included during each half.

But temperatures were still nudging 39 degrees at kickoff and 35 degrees when the match finished.

Glory winger Chris Harold lasted only 25 minutes before being subbed off with heat fatigue.

"Some players have since reported heat illnesses, including excessive weight loss, headaches and vomiting," PFA chief executive Adam Vivian said.

"The PFA will continue to monitor the players' health and will be conducting further discussions with FFA 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."

Perth's next A-League fixture against Melbourne Victory is scheduled to kick off at 5pm on 25 January - a time of year when temperatures in excess of 40 degrees Celsius have been recorded.

Glory has already put in a request to have the game pushed back to 6.30pm.

Perth skipper Michael Thwaite said Monday's match should have been played at night.

"We can't be stupid about these things when you've got players' health risks," Thwaite said.

"When you've got Chris Harold coming off after 20 minutes, it goes to show some players are going to react differently."

Vivian acknowledged FFA's heat policy was superior to that of world governing body FIFA's in terms of player health and safety.

But he said the PFA would continue working with experts to ensure it improved even further.

"Having been a clash between two of the competition's most outstanding teams, the players were desperate to put on an outstanding spectacle," Vivian said of Monday's match, which Adelaide won 2-1.

"Post-match the players have expressed their disappointment that their efforts were effected by the conditions."