Brian O'Driscoll insists the current length of British and Irish Lions tours must be preserved if they are to remain viable.
The number of fixtures could be slashed from 10 to eight or even five if the game's powerbrokers target the Lions in their bid to create space for the new global season, which is to commence from 2020.
O'Driscoll, who led the elite of British and Irish rugby to New Zealand in 2005 and is a veteran of three other tours, insists any reduction in games would severely impact chances of toppling the southern hemisphere giants.
"They're not viable if you start condensing them," said O'Driscoll, who was speaking on behalf of Land Rover, a principal partner of the British and Irish Lions.
"You can't condense them any further than has already been done if you want to pull together as a team for a scenario that shouldn't work but has worked in the past.
"In my experience from the four tours I've been on it works because people are able to buy into it, but you need a little bit of time to bed in.
"As it stands there are only four weeks before the first Test and you have to give the opportunity to get combinations working together so that players can develop that element of telepathy.
"If you're reducing that to five weeks, a couple of weeks leading into the first Test, it will be more difficult to take on one of the superpowers.
"Something will have to give, of course, and player welfare is vitally important, but some of the traditions of the game need to be upheld.
"The Lions is one of the really important and special traditions from a player perspective having been on a few tours myself."
O'Driscoll sees Elliot Daly as a potential bolter to make this summer's tour to New Zealand.
Daly raced in the match-winning try in England's 21-16 victory over Wales on Saturday and O'Driscoll believes the versatility of the Wasps flyer, who covers wing, centre and full-back, gives him a good chance of making Warren Gatland's squad.
O'Driscoll's view of Daly's Lions prospects is similar to that of former Wales and Lions wing Shane Williams, who earlier on Wednesday backed the 24-year-old for a Test starting spot in New Zealand.
Former Ireland captain O'Driscoll said: "Elliot can make it the way he is going. Sometimes in Test match rugby being a utility back can work against you - on Lions tours it can work for you.
"If you can play multiple positions it can definitely be an advantage on those 50-50 calls.
"The coach will go with someone who can offer a little bit more, midweek as well as for the Test matches. It breaks the mould of working against you when it comes to the Lions."