"If you look at the spinners at the moment in Australia - he is the best," Warne told The Daily Telegraph.
"He has slowed his pace down and is spinning it beautifully.
"Being 36 is an advantage for him experience wise and he has basically played club cricket once a week for most of his career so his body isn't a worry. I don't see it as a backwards step that Beau Casson is gone. This is a tour of India and they have really good players of spin and we don't want to ruin anyone," Warne added.
Long-time Victorian club cricketer McGain, 36, was yesterday named as Australia's frontline spinner for next month's arduous four-Test Indian tour and will partner rookie Tasmanian off spinner Jason Krejza in a 15-man squad.
Former information technology worker McGain will become Australia's oldest Test debutant in 24 years.
Warne says he is happy in his business life, and playing professional poker, but again refused to completely hose down comeback speculation.
"In my life I've learnt never to say never," Warne said.
"But at the moment I'm very happily retired and I'm very happy with my life."