But after the match, the two playing groups put on a united front.
The two teams formed a big circle and linked arms in the middle of the pitch shortly after the whistle.
And the Rebels accepted the Force's invitation to join them for a changeroom beer, allowing players from both sides to open up to each other about the situation affecting their respective clubs.
McGahan has already announced he will be stepping down as head coach at the end of the season.
Assistant coach Morgan Turinui said the Rebels remain confident of surviving the axe, adding it was important for players not to enter the Jaguares clash with the mindset that the franchise will fold.
"Denial possibly is a powerful thing next week," Turinui said.
"We've got some pretty important people to the Rebels club leaving.
"Tony will be leaving after four years as head coach. Probably no staff member has had more influence on the club in its history than what Tony has.
"I think it's important for the group and the staff to send him off in the manner he deserves.
"And Mitch Inman has a possibility of playing his 100th game of Super Rugby.
"Those sort of mini internal things are good opportunities to motivate our players and have a good mindset around the finish."
The Force will also have plenty of motivation in Saturday's home match against the Waratahs, with foundation player Matt Hodgson playing his final game.
The Perth side appeared dead in the water when the ARU first announced it would cut a franchise in April. But it now appears the Rebels are more vulnerable.
"A lot of people thought the Western Force was just going to roll over and die," Force coach Dave Wessels said.
"I don't feel like we've done that, so I'm proud of the boys for that.
"They kept fighting. We're still fighting. I think that's maybe surprised a lot of people." Wessels said the post-match circle on the pitch wasn't planned.
"I think the players just did it themselves," Wessels said.
"We have a lot of sympathy for how the Rebels players are feeling, and probably vice-versa.
"It's just a bizarre situation that we're all in."