Waratahs flyhalf Bernard Foley has been ruled out of the side's opening round clash with the Force.
Foley is still feeling the effects of a head knock suffered in the Waratahs' trial loss to the Highlanders.
"He's still suffering some dizziness and so forth," coach Daryl Gibson said.
"Then obviously his cognitive tests that they do on the computers, he wasn't passing that as well."
Foley’s replacement comes in the form of Bryce Hegarty, the former Rebels flyhalf-fullback, who has earned the moniker ‘Fettuccine’ since coming to Sydney.
“The reason he's so popular is he doesn't look like he should be playing 10 or rugby, in a really nice way,” Gibson said.
“We call him Fettucine, which is a reference to his legs because they're like spaghetti and they look like they're going to fall off at any moment but he can play the game."
Hegarty missed most of 2016 after rupturing his ACL, but ran in the playmaker spot for most of the preseason with Wallabies 10, Foley, still on his off-season break.
"The reason we recruited Bryce in the first instance was because of his experience and the number of years he's played at the Rebels and we get an excellent replacement and someone who can really step in and run the show," he said.
“He's got wonderful game sense, good skill set, excellent rugby brain and I think that's the thing that attracts me to him, is he gets the game, he's a rugby player.
“While he doesn't have all the talents in the world, he utilises every ounce of it.”
Waratahs fullback Andrew Kellaway admitted Foley’s would be a big loss, but believes Hegarty will step into the position with ease.
“I think Bernard’s a world-class player so losing him is disappointing but Bryce is a great footballer and he’s actually been here all preseason, he’s pretty much led the boys all preseason so it’s a pretty seamless transition for us,” he said.
“He’s a very hungry competitive guy, so to see him get his crack’s awesome and it’s going to be great to be out there with him.
Lock Ned Hanigan has also been ruled out with a knee issue, an injury that Gibson said would keep him out for two weeks.
The shifts mean that former Reds and Sharks second rower Dave McDuling will come onto the bench for the clash, with David Horwitz replacing Hegarty.
The Waratahs take on the Force on Saturday night, kicking off at 7:40pm AEDT.