Melbourne coach Dave Wessels said Maddocks had a few niggles and also needed a mental refresh.
“He’s a big part of our team but at this stage he’s played a lot of rugby and there’s some warning signs his body was starting to feel a bit fragile,” Wessels said.
The Rebels currently sit eighth – and must at least hold that spot through the final round to play in their first finals campaign.
“It’s showtime for us,” said Wessels.
“We’ve got an opportunity to do something for the club that we’ve never been able to do so I think guys are pretty motivated.”
The Rebels were crushed 66-0 last round by the front-running Crusaders but Wessels said his team had quickly put that “embarrassing” loss behind them.
Resting Genia and starting Cooper on the bench last round, Melbourne were always targeting the Chiefs match as the one to cement a playoff berth.
Currently 11th, the Chiefs are also in the finals hunt and require a bonus point win to assure themselves a spot in the top eight.
“When we first looked at the calendar this was a game that we thought we’d want to target,” Wessels said.
“It’s an opportunity to respond from last week … I feel like we are going to play well on Friday night.”
Rebels: Dane Haylett-Petty (c), Reece Hodge, Tom English, Billy Meakes, Marika Koroibete, Quade Cooper, Will Genia, Isi Naisarani, Richard Hardwick, Angus Cottrell, Luke Jones, Matt Philip, Jermaine Ainsley, Anaru Rangi, Tetera Faulkner. Reserves: Jordan Uelese, Matt Gibbon, Sam Talakai, Ross Haylett-Petty, Rob Leota, Michael Ruru, Matt Toomua, Campbell Magnay.
Sign up to our mailing list here and we’ll keep you up to the minute with weekly updates from the world of rugby.