The veteran French defender, who joined the A-League club as a marquee signing in October last year, was involved in a training pitch bust-up with Kenny Lowe's assistant Andy Ord in the wake of last weekend's 2-0 home loss to the Western Sydney Wanderers.
The Western Australian outfit held a Members Forum on Wednesday night to discuss the direction of the club but Brewer insists that the Gallas incident was not even raised.
"The signing of William Gallas was something (former coach) Alistair (Edwards) drove and at one level that's seen as contradictory to our strategy, but the role he plays in developing players among the environment is crucial," Brewer said.
"Ask the players how much they've learned from his professionalism.
"That's justified given the massive void between the young teenage players or 18-21 age bracket and then there's the 30-plus group."
Since arriving at the nib Stadium, two-time Premier League winner Gallas has made a total of eight appearances for the Glory.
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