The tourists will play five matches Down Under - against the Western Force, Queensland Reds, a combined New South Wales/Queensland XV, NSW Waratahs and ACT Brumbies - before the series opener.
But the Suncorp Stadium clash will be the Wallabies' first Test match in 202 days, and Deans said: "There's no doubt that the Lions will have a huge advantage in terms of entering the series."
He added: "You go back to 2001 and the Wallabies had similar time (to prepare) but with a (warm-up) game, so it was obviously a more complete prep and they got spanked in the first Test.
"And (former Wallabies coach) Rod Macqueen, who spoke with us recently, quite openly conceded that (the 2001 team's) preparation wasn't adequate, and he's genuinely concerned by what we're confronted with."
The Australian provinces are furious over the decision to quarantine Test players from Round 17 of Super Rugby in preparation for facing the Lions but an unapologetic Deans says preparation for the Lions series must take priority.
The Brumbies host the Force on June 7 while the Waratahs travel to Perth to face the Force on Sunday, June 9. It is conceivable either clash could decide the finals fate of at least one Australian club and ARU chief executive Bill Pulver has left the door ajar for some players to be released back to their teams on a 'case-by-case basis'.
But Deans made it clear he wants his best Wallabies available to train for the entire three-week training window.
"A call has been made, there'll be a preparation and if I was a franchise coach I'd be looking to control the controllables," Deans said. "It will still be the shortest preparation in the history of the game for a Lions series so we will want the group with us to prepare solely.
"Obviously the door's been left open to some extent around circumstance at the time, but if I was a franchise, and I've been in that context myself and we understand they've got campaigns of their own that they want to do well in, but I guess the key is the 15 rounds leading up to that not the one round at that time."