With tighthead prop Taniela Tupou suffering a calf injury at the weekend, Rennie's point could not have been better timed.
Tupou's injury could keep him off the field until the middle of next month, effectively ruling him out should the Reds qualify for the Super Rugby Pacific final. That would reduce his chances of preparing for Australia's three-Test series against England in July.
While in Melbourne publicising the staging of a Bledisloe Cup Test at Marvel Stadium this year, Rennie said that the challenge Australia rugby faced was keeping its players fit and healthy.
That was because New Zealand enjoyed greater player depth from which it could make injury replacements.
"It's important we do well against the Kiwi sides," he said.
"It gives us confidence, gives our players confidence to know that playing against some of the best players in the world, and they can stand up."
But the challenge was for Australia's Super sides to develop a level of depth that made them consistently competitive with benefits for the Test side.
"We'd be confident we can pick a really strong 23. Our Wallabies bench could add value.
"That's crucial against the All Blacks because they've got so much depth," he said.
One area where there was undoubted depth was at flanker. Skipper Michael Hooper had recovered from a foot injury, while Fraser McReight was performing well in Super Rugby.
"His continuity has gone to another level, and, as we know, he's very good post-tackle, although he needs to make sure he's disciplined around that, as he's given away a few penalties.
"He's worked really hard on his defensive game, so he's doing everything he can.
"Guys like Fraser are massive for us, not just in the depth but the quality of our Super games, our Super teams, and our ability to be competitive.
"You want guys who are going to fight for a spot," he said.