And now Munster must fight on all fronts without their influential prop, this weekend the 2006 and 2008 Heineken Cup champions are looking to be the first team to automatically progress to the last eight with a bonus point victory over Castres.
But despite not having Hayes alongside him in the front row anymore, Varley believes the Bull's influence can still play a role.
"It will seem a little strange not having John around the dressing room, but all teams evolve and move on," said Varley.
"When we played against Northampton Saints in round one it was the first time we hadn't had an Anthony Foley, Alan Quinlan, John Hayes or David Wallace in the starting line-up.
"John has been such a massive part of Munster rugby for the past 14 seasons, but that's sport - guys move on.
"John has passed on a massive amount of knowledge and experience to the younger players and will continue to be an inspiration to all of us.
"He spoke to us in the dressing room after his final appearance, in the game against Connacht Rugby over the Christmas period, and told us what it had meant to him to wear the Munster jersey.
"His values will be carried on by those who remain and none of us will ever take for granted our place in the side or the shirt we pull on."
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