Veteran Australian opener Warner will earn his 112th and last Test cap when Australia hunts a 3-0 series whitewash against Pakistan in Sydney from Wednesday.
Warner's career in the baggy green began with concerns he was too brash a batsman to succeed in Test cricket and ends with more runs to his name than any other Australian opener in the long game's history.
His attacking style has been his calling card, most recently earning him a pivotal century in the series opener against Pakistan in Perth.
McGrath is hopeful of seeing that same Warner one last time at the SCG.
"Go out, be positive," the legendary quick said when asked of his advice for Warner.
"We saw him come out and get a good hundred over in Perth, just going back to the way he plays.
"Hopefully he can go out on a high. It'd be great to see him get a hundred here in front of his home crowd."
McGrath, Shane Warne and Justin Langer called time on their own Test careers following the SCG Test in 2007 - a 10-wicket drubbing of England that confirmed Australia's 5-0 Ashes whitewash.
McGrath's memories of that match informed his words of wisdom for Warner.
"You're a long time retired, and I guess I only had one fear when I played, and that was if I walked off the field at the end of the day and didn't back myself on the field," he said.
"I love seeing sportspeople go out and play without fear and I think he does that."
Warner said he hoped to be remembered as a player who had remained true to himself and "someone who has gone out there and just given it his all".
"(I was) a boy from housing commission having a dream," he said.
"I've not always fitted the mould, but I've been authentic and honest.
"I think that shows you on the field in Test cricket, I've played the exact same way.
"I'm even playing lap shots like I do in T20 cricket. I'm still trying my best to get better even in this last Test. I'm hungry to score runs.
"I just want to leave behind that you can go out and play the way you want to play."
Warner's swansong coincides with the 16th iteration of the McGrath Foundation's Pink Test, a fundraising initiative aimed at helping provide breast cancer patients with nurses.
Established by McGrath and his late wife Jane, the charity is again running its virtual pink seat initiative to encourage fans to buy a place at the SCG even if they are unable to attend the Test.
"This year, we've set a goal of 322,000 virtual pink seats, which means we'll basically achieve our mission of (employing) 250 McGrath breast care nurses," McGrath said.
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