The Lions legend, who has been a coach on four tours, believes Gatland has "one hand tied behind his back" with the Aviva Premiership and RaboDirect PRO12 finals taking place on May 25.
Gatland's charges gather as a full squad the following day and jet to Hong Kong the following day - the shortest preparation time in the Lions 125-year history.
"It is short-sighted and unfair," McGeechan told the Telegraph.
"It's extremely disappointing that they did not take up on that. They could have had a couple of midweek domestic matches during the season and finished a week earlier.
"They have to be big enough to do these things properly. The Lions is the biggest thing in a player's mind. It's the biggest rugby event too in the eyes of spectators. Tickets were snapped up in minutes.
"There will always be time constraints. But give Warren a week before departure. That would not be perfect but it would be fair.
"What we've done instead is build in unfairness. He faces an even bigger challenge in that regard than I did in 2009. Does he leave with one hand tied behind his back? Yes, I believe he does.
"We should be looking to do all we can to help the Lions and in this regard we haven't.
"What has surprised everyone is that the whole notion of the Lions has actually got bigger in the professional era when everyone thought it would struggle. There is an excitement and magic there that supporters have latched on to, players also."
Gatland announces his 37-man squad on April 30, following the semi-finals of the Heineken and Amlin Challenge Cups.
And McGeechan reckons the return to form and fitness of 2009 skipper Paul O'Connell may lead to a reshuffle of the party and even a rethink of the captaincy.
"There is a dilemma there now," added McGeechan, who chose O'Connell to lead the Lions in 2009.
"Warren will know what he wants but Paul's availability has possibly thrown a spanner in the works. A Lions captain has to be more than a national captain.
"He has to have a real feel for what the Lions is all about. Paul's performance against Harlequins in the Heineken Cup was a real statement from him. It showed that he has got the energy, the attitude and that he wants to be involved."
McGeechan is also critical of the Australians for deciding to mothball their test players by withdrawing them from the provincial matches.
"That does disappoint me," said McGeechan, who signed off with a backing for Gatland's squad to return with a series victory.
"The Lions have great quality and I believe they will win."