Former British & Irish Lions head coach Ian McGeechan has warned his successor not to repeat mistakes of the past and select players just on their reputation.
Warren Gatland, the new Lions head coach, will announce his squad to tour Australia on 30 April and McGeechan is confident the New Zealander is the right man to make the tough calls.
McGeechan, who had Gatland as his assistant coach in 2009, is still an advisor to the Lions and believes the squad should be chosen on form over the last three months, while any player carrying an injury should not be on the plane.
McGeechan told the Press Association: "You need to take fit players. With only a six-week preparation period you can't have players carrying injuries or players out of form.
"That's the big call for the coaches, picking fit players who are on form who can then come together, so you are working with what you want to do right from the word go with players doing every training session and available for games.
"You can't find form and if you are injured you haven't got the time.
"That's been the mistake in the past, in that players who have not been in form or have been injured have gone because the coach thinks he's the best player in the position based on reputation, not performance.
"I think the three months prior to the tour is the critical period."
Wales coach Rob Howley will also be on the Lions coaching staff for a second tour, along with Andy Farrell and Graham Rowntree, and McGeechan says continuity is an important factor.
He said: "When you are trying to put together a top-class, world-class Test team, if you have got that little bit of continuity you are away from first base straight away.
"I think Warren Gatland was the right appointment, he's an outstanding coach but he also understands the Lions and has experience from 2009. So it will be lot of similar management people and maybe a third to a half of the players.
"You are not starting from scratch knowing you have five weeks to be Test match ready."
The Lions have not won a series since 1997 and McGeechan admits it is a tough task to put together a winning squad from four countries.
He said: "You are playing southern hemisphere countries who take it all pretty seriously anyway, they have had years to put a team together.
"They are bedded in and know what they are doing. The Lions have high-quality players but what you have to do is work out the best way of getting that talent to show in Test match conditions.
"Sometimes it's about not over-complicating it, it's being very clear and straightforward about what you want.
"The downside of 2009 is that we didn't win the series. The upside was that we probably played the best rugby seen anywhere in the world that year, and in retrospect that's something you get satisfaction from.
"Some of the combinations were fantastic - Jamie Roberts and Brian O'Driscoll were probably the best centre partnership in world rugby that year."
Gatland is expected to take between 35 to 37 players and is keeping a close eye on a number of injured players including Ireland's lock Paul O'Connell and wing Simon Zebo, Wales flanker Dan Lydiate and England prop Alex Corbisiero.
He has revealed he will not let any of the players know if they have been selected before it has been announced to the public.
Gatland told the Daily Telegraph: "That is how it was traditionally done. I can remember an All Blacks squad being announced on the radio while I was driving a car and hearing that I was in the squad. I nearly drove off the side of the road."