Warburton is expected to be unveiled as captain when his former Wales boss Warren Gatland announces his 38-man squad to tour Australia at 11am.
And McGeechan, who toured four times, has backed the anticipated choice of a first Welsh captain of the Lions in 36 years.
“I think he [Warburton] would be Warren’s favourite,” said McGeechan. “You do have to have that captain-coach relationship because you need to be honest and get really good feedback and you need trust both ways – what you are thinking about and how you are developing things.
“You need someone you feel you know well. That is the obvious combination. It’s a great challenge and a huge responsibility because you are heading up four countries and you have to be comfortable with that. If he is happy with that in his head, then he’s favourite.”
Warburton, 24, is also the popular choice with bookmakers and is expected to hold off the challenge of Irish rivals Paul O’Connell and Brian O’Driscoll.
England captain Chris Robshaw is sweating on his inclusion in the squad, as is international team-mate Chris Ashton following an indifferent Six Nations campaign.
World Cup-winning fly-half Jonny Wilkinson has played his way into surprise contention, with a virtuoso performance in Sunday’s Heineken Cup semi-final for Toulon.
However, the former England No10 will turn 34 before the trip Down Under and has suggested Gatland would be better off picking younger fly-halfs like Owen Farrell, 21, or Wales kicker Dan Biggar, 23.
LIONS ON TOUR
Sat Jun 1, Barbarians, Hong Kong
Wed Jun 5, Western Force, Perth
Sat Jun 8, Queensland Reds, Brisbane
Tue Jun 11, Combined Country, N’castle
Sat Jun 15, NSW Waratahs, Sydney
Tue Jun 18, Brumbies, Canberra
Sat Jun 22, First Test: Australia, Brisbane
Tue Jun 25, Melbourne Rebels, M’brne
Sat Jun 29, Second Test: Australia, Melbourne
Sat Jul 6, Third Test: Australia, Sydney