Strength of tour squad hinges on upcoming clashes with fringe players to get game-time.
British and Irish Lions coach Warren Gatland said players who have no involvement in upcoming domestic and European finals could give themselves an advantage when it comes to gaining a place for the first Test against Australia.
Gatland added he faced a nervous wait over the next few weeks with, several of his 37-man squad involved in major club matches for Ulster, Leinster, Leicester and Northampton.
Those players not involved in those club finals will be the ones who will face the Barbarians in the Lions’ tour opener in Hong Kong on June 1.
“The first three-and-a-half weeks will be about preparation for the first Test,” Gatland said.
“The players that prepare for that first game (in Hong Kong) are going to have the biggest advantage on tour.
“They are the players not involved in the finals so they are going to have the best preparation in the next couple of weeks. The players coming back from finals are going to be at a disadvantage because of their lack of preparation time.
“So, the team that plays the Barbarians should be in reasonable shape in terms of their preparations in the next couple of weeks.”
But Gatland insisted he did not want players holding themselves back while on club duty in order to save themselves for the Lions.
“It’s tough for the players in terms of they know a few days after a big game they are on the plane,” he said.
“There’s a bit of trepidation about not picking up injuries. But if you go in with that attitude and try and look after yourself there is more chance of picking up an injury.
“So the advice to those players is to go hell for leather.”
After the Barbarians match, the Lions travel to Australia where they play four more tour games before the first of three Tests with the Wallabies in Brisbane on June 22.
The Lions, made up of players from England, Scotland, Ireland and Wales, have not won a Test series since defeating South Africa in 1997.