Robin McBryde says there is still an opportunity for players to play their way into the British and Irish Lions and Wales squads if they impress at Judgement Day.
McBryde leads Wales against Samoa and Tonga this summer in the absence of Warren Gatland and Rob Howley, who coach the Lions in New Zealand.
"The game on Saturday gives players a stage to be measured," he said.
"We'll see how they react to pressure of playing at the Principality."
Cardiff Blues face the Ospreys at the Principality Stadium on Saturday before the Newport Gwent Dragons play the Scarlets in the double header with Gatland naming his Lions squad on 19 April.
"I can only speculate in regards to the selection on the 19th [of April] for the Lions," said McBryde.
"We are just expecting there to be a few players from the teams that are playing this weekend to be selected.
"But we are just looking forward to seeing how they react to playing at the Principality and looking forward to the good occasion.
"There were some quite consistent performances during the Six Nations, so there could be as many as 9/10 Welsh players selected for the Lions tour."
Strong Wales squad
McBryde says he will be picking a squad to win both Tests when he names the Wales touring party for the summer of 24 April, and that Judgement Day could also have ramifications for the Wales squad.
"We have always said that we would measure the players by their performances in the Pro12, their performances against one another in the derbies and in Europe, especially against the Irish provinces." he told BBC Wales Sport.
"But this game is a big one from a selection point of view. We are looking to name the squad on the 24th to allow the players to prepare both physical and mentally prepare for the tour ahead. So the double-header does allow us to focus on the players with a close microscope.
"We are going there with the mentality to want to win both Tests. That is in the forefront of our minds and the selection will be based on this.
"We can't control injuries or players being asked to join the Lions, we know we can't account for that.
"We can take a strong squad down there and make sure our squad is right for the two games against Samoa and Tonga.
"Maybe there will be one eye on the short term and one eye on the long term with the World Cup just two years away."