Knowing the value of his Wallabies teammate Michael Hooper, Melbourne's Dane Haylett-Petty expects the Waratahs to be hit hard by the loss of their injured skipper when the teams meet in a crucial Super Rugby showdown on Friday night.
Melbourne host the Australian conference-leading Waratahs at AAMI Park with just one point separating the teams with three rounds remaining before finals.
The Wallabies captain injured his hamstring early in Australia's Test loss to Ireland last Saturday, ruling him out of his team's charge to the finals.
The Rebels have their own injury concerns with Will Genia (arm) and skipper Adam Coleman (abductor) sidelined.
But their respective replacements Michael Ruru and former British and Irish Lions representative Geoff Parling have had plenty of game time.
Hooper, however, has been a vital cog in the Waratahs' success, only missing a miserly 53 minutes of play in his 93 games since joining them in 2013.
The injury brings to an end his run of 79 consecutive Super Rugby matches for the Waratahs.
"He's hugely valuable and I think it's going to be quite a big test for the Waratahs," Haylett-Petty said.
"It's been five or six years since he's missed a game and he's probably the main voice in that group so it will be interesting to see how they go without him."
Haylett-Petty will return to fullback after playing on the wing for the Wallabies with the Rebels making minimal changes from their last Super Rugby win over the Blues before the June Test break.
Prop Ben Daley will make his first start for the season and is joined by Sam Talakai.
On the bench, hooker Nathan Charles returns to the playing 23 following Jordan Uelese's season-ending knee injury while Jack Debreczeni also makes his first Super Rugby appearance since the win over the Brumbies in early May.
Rebels: Dane Haylett-Petty, Jack Maddocks, Tom English (c), Billy Meakes, Marika Koroibete, Reece Hodge, Michael Ruru, Amanaki Mafi, Colby Fainga'a, Angus Cottrell, Geoff Parling, Matt Philip, Sam Talakai, Anaru Rangi, Ben Daley. Res: Nathan Charles, Fereti Sa'aga, Jermaine Ainsley, Ross Haylett-Petty, Lopeti Timani, Harrison Goddard, Jack Debreczeni, Sefa Naivalu.