Nor will Rafter be shocked if Kyrgios flops and crashes out in the first round in his much-anticipated major return at Melbourne Park month.
Australia's former Davis Cup captain believes it's impossible to predict how his ex-charge will fare on his competitive return after more than two years off tour with career-threatening wrist and knee injuries.
Kyrgios will make his comeback at the Brisbane International from December before returning to the grand slam stage at the Open starting on January 12.
The 29-year-old needed an injury-protected ranking to secure a direct entry to the Open but Rafter - who handed a teenaged Kyrgios his Davis Cup debut in 2013 - says it would be foolish to dismiss the mercurial talent's prospects of a deep run.
"You'd never write anyone off with the talent that Nick has. It's pretty amazing," Rafter told AAP.
"I really don't know what he's done, though. A year and a half off the game ... so it's going to be interesting.
"I have no expectations or no understanding about how he is going to go."
Kyrgios has played only one tour singles event since reaching the 2022 US Open quarter-finals, seven weeks after losing to Novak Djokovic in the Wimbledon decider.
The 2022 US Open was Nick Kyrgios's most recent grand slam singles campaign. (AP PHOTO)
Rafter, though, believes the now-unranked former world No.17 could still be a factor at the Open, where his best result was the quarter-finals way back in 2015.
"He's got a massive game," Rafter said.
"But then can he keep it together? Can his body hold up? Can his mind hold together?
"They're probably his really big hurdles, especially his body.
"If you don't play competitively, God, it's a completely different thing than to training."
"So I really don't know what to expect from him. I think it's all up in the air.
"If you go there to see him play, it will be interesting to see.
"I don't know quite what the expectation is from the pundits but my expectation is there is none.
"When I say there is no expectation, if he gets to the quarters, the semis, it wouldn't surprise me.
"If he loses the first round, it wouldn't surprise me. I don't know."
Rafter also has no idea how fellow former Australian tennis bad boy Bernard Tomic will fare on his return to Melbourne.
After slumping to No.825 in the world in late 2022, Tomic has toiled away admirably on the low-level tours in the Americas to hit 200 in the rankings in October and clinch an Australian Open qualifying berth.
Bernard Tomic has earned a return to Australian Open qualifying. (Luis Ascui/AAP PHOTOS)
Rafter couldn't believe it when told Tomic, a one-time world No.17 and Wimbledon quarter-finalist, was now 32 years of age - and still playing.
"Bloody hell," said the former world No.1 and two-time US Open champion.
"Thirty two? It's good to see Bernie have a crack.
"I haven't see him play in years. Let's have a look, see how he goes."
Tomic most recently made the Australian Open draw, for an 11th time, in 2022 when he was the only Australian of 20 hopefuls to successfully qualify.
