On Sunday, Bennell, Matera and McKenzie failed to meet the standards outlined by the coaches and endorsed by the players following Saturday evening’s victory over the Brisbane Lions.
The GC SUNS senior management, coaches and player leadership group unanimously support the decision.
General Manager of Football Operations, Marcus Ashcroft, confirmed the outcome.
"The player leadership group advised the coaches on Monday that they had challenged a group of players who had failed to live the standards agreed upon following Saturday's match.
"Harley, Brandon and Trent individually acknowledged to the leadership group and senior coach that they failed to meet the standards outlined.
"It was the shared view of the leadership group, coaches and senior management that the players would be unavailable for senior selection this week,” Ashcroft said.
Senior coach Rodney Eade said the players and coaches were left disappointed and frustrated with the trio.
"We had clear expectations and we are extremely disappointed and frustrated that Harley, Brandon and Trent didn't meet these standards.
"We have been encouraged that the majority of the playing group have made progress in living the attitudes and behaviours required to be an elite AFL player and team.
"However those who don't live by the team's standards will be made accountable, no matter who they are.
"The actions of Harley, Brandon and Trent will leave us incredibly bare on the field this week, but this tough decision reflects the direction our club is heading and we can't compromise that,” Eade said.
Acting captain Michael Rischitelli said the view of the coaches and senior management was consistent with the players.
"We all understood and agreed on the standards outlined after the game and we feel let down by Harley, Brandon and Trent.
"We expect Harley, Brandon and Trent to accept their punishment and importantly respond accordingly going forward," Rischitelli said.