Waratahs coach Darren Coleman has revealed Nawaqanitawase had suffered a hamstring strain at training and is doubtful to Saturday night's showdown with the defending champions at AAMI Park.
"He is having scans and receiving treatment, and we will give him until later in the week to prove his fitness," Coleman said on Wednesday.
"We're fortunate that Triston Reilly has successfully recovered from his ankle injury, and he will come into the starting side if Mark is unable to play."
Nawaqanitawase was one of the few bright spots in an otherwise lacklustre display from the Waratahs in their season-opening 40-22 loss to Queensland.
The X-factor attacker set up a try and posed a constant threat to the Reds.
With Wallabies teammate Izaia Perese already ruled out because of concussion protocols, Coleman can hardly losing Nawaqanitawase when his side takes on a Crusaders outfit also coming off a loss and coached by Waratahs discard Rob Penny.
Penny was unceremoniously shown the door after NSW's historic winless 2021 season and will surely be plotting revenge.
In better news for the Waratahs, key forwards Hugh Sinclair and Ned Hanigan will make comebacks from injury.
The Waratahs' Ned Hanigan (R) contests a lineout against the Blues during the 2023 season. (Lynne Cameron/AAP PHOTOS)
The return of 2022 Wallaby Jock Campbell, meanwhile, is the lone change to Queensland's starting side looking to bust an 11-year hoodoo against the Hurricanes on Sunday.
Reds coach Les Kiss somewhat contentiously couldn't find a place for Campbell last weekend but has named the fullback on the wing in place of Mac Grealy as they chase a first win over the Hurricanes in more than a decade.
"Jock gets his chance this weekend after his brilliant form in the trials. This is an opportunity for me to see him as a winger," Kiss said."It's great to have such riches in the backline."
The Western Force will welcome back captain Jeremy Williams for Friday night's derby against the Melbourne Rebels.
In one of three changes, the newly-appointed skipper returns to lead the Force for the first time after missing round one with concussion to boost the side's lock stocks.
Feleti Kaitu'u and Ryan Coxon have also been added to the 23-man team, with the suspended Marley Pearce, plus Titi Nofoagatotoa and Ben Funnell out of the side that lost to the Hurricanes.
Rebels coach Kevin Foote has made five changes, including promoting 51-Test Wallaby Taniela Tupou and hooker Alex Mafi move to the starting front row.
After bringing spark off the bench in a disappointing 30-3 loss to the Brumbies last week, James Tuttle will get his first start for the '24 season at halfback while Matt Proctor makes his debut for the Rebels at outside centre with Filipo Daugunu shifting to the wing.
Brumbies coach Stephen Larkham has made just one tweak to his side to face the Chiefs on Sunday, with prop Sosefo Kautai named to start.
