UPDATED: Get the best XV on the park.
That's the simple theory behind a new-look Waratahs backline that has seen Kurtley Beale shift to fullback, Karmichael Hunt and Adam Ashley-Cooper in the centres and Israel Folau on the wing to face the Reds.
Beale hasn't played fullback for the Waratahs since 2014, though it was his primary role for the Wallabies during the Rugby World Cup in 2015 and Cron said the shifts were just about ensuring all of those players were in the starting time.
"Those guys have all come in fit and it's about getting our best on the field," he said.
"So, we think for this game against the Reds, those boys in those positions is our best team to play against them.
"That's really the reason for the changes."
While Folau has previously voiced his preference for the fullback spot, Cron said the superstar was happy to move for the good of the team.
"One thing about Izzy is he's a massive team man, so whatever's best for the team, Iz does and you probably hear him talk about that all the time," he said.
"For him, it opens up some opportunities for him. It puts him in a position to potentially get some ball first phase and also on any sort of kick-attack stuff, so for him he's pretty fine with it."
The Waratahs' fluidity in attack, that allows a host of those players to come into first and second receiver and switch around in attack and defence, means the numerical changes aren't necessarily as drastic as they seem.
"From fullback, any of our fullbacks have the opportunity to step in and be a first receiver, second phase, third phase," Cron said.
"KB's that guy, he loves getting his hands on the ball so I've got no doubts he'll come in and get a lot of pill."
Returning hooker Tatafu Polota-Nau will make his comeback off the bench after joining NSW on a short-term loan, in the only change to the forward pack.
"I think day three he came in and his eyes were cross-eyed, he said he'd seen enough (tape)," he said.
"He'd taken in quite a lot because there is a bit, learning, but I think he's done it so many years and so many times now, moving from even a Super Rugby team even an international to the Wallabies, you've only got a week sometimes to learn all your new systems.
"So he's got himself down pat around how he does that."
Polota-Nau's return has already been valuable, according to Cron, with the hooker helping the next generation in training.
"The key thing around Taf is the door kind of opened with us with Leicester and the opportunity for him to come back, so we took it," he said.
"He's come back in, he adds an enormous amount of experience, he adds a really big body for us and he's, if you look at him in training, he sits on the field 20 minutes after training just talking to a lot of the younger boys who can learn a lot from him.
"One of the biggest things in rugby is having that top tier leadership group pass on their knowledge, especially in the forwards.
"t's a really good opportunity for the guys in the time that we've got him here for them to get a lot of experience .What he does add for us is a huge body in the middle of that pack and he's got a really good nature about him around the teaching of other players.
"He's a no-brainer pick for us."
Halfback Nick Phipps is still missing with a preseason calf injury but Cron expects him to be back in the mix for round five.
"Still medically - it's based off how much running he's done," he said.
"It's just making sure that - you can play him but there'll be risks and I think it's about mitigating the amount of risk for him and the guys' medical team and the athletic performance coaches have decided we're probably a week early in that one.
"I think give him the extra week and make sure he's 100 per cent."
The Waratahs take on the Reds on Saturday night at the SCG, kicking off at 7:45pm AEDT, LIVE on FOX SPORTS and via RUGBY.com.au RADIO. Buy tickets here.
IN: Tatafu Polota-Nau
OUT: Tolu Latu
Waratahs to face Reds
1. Harry Johnson-Holmes
2. Damien Fitzpatrick
3. Sekope Kepu
4. Jed Holloway
5. Rob Simmons
6. Ned Hanigan
7. Michael Hooper (C)
8. Jack Dempsey
9. Jake Gordon
10. Bernard Foley (Vc)
11. Curtis Rona
12. Karmichael Hunt
13. Adam Ashley-Cooper
14. Israel Folau
15. Kurtley Beale
16. Tatafu Polota-Nau
17. Rory O’Connor
18. Chris Talakai
19. Lachlan Swinton
20. Will Miller
21. Mitch Short
22. Mack Mason
23. Alex Newsome