Wales head coach Warren Gatland has no doubt his players understand the importance of Saturday's Millennium Stadium clash against Ireland as a fierce battle for World Cup squad places intensifies.
Gatland reported a "couple of little niggles and fights" among the forwards at training on Tuesday, with Wales having entered the competitive warm-up phase of their World Cup countdown.
He will name a final 31-man World Cup party on August 31. Wales face home and away appointments with Ireland before then.
England Under-20 World Cup winner Ross Moriarty is among four players handed a Wales debut on Saturday, when he will be joined by Ospreys wing Eli Walker, Newport Gwent Dragons centre Tyler Morgan and Bath lock Dominic Day.
St Helens-born Gloucester flanker Moriarty, whose father Paul and uncle Richard both played for Wales, helped England win successive Under-20 World Cup finals in 2013 - against Wales - when his team-mates included current senior England stars Anthony Watson and Jack Nowell, and 2014.
Moriarty is not tied to England because he has not represented either the senior team or England's designated second XV, the Saxons.
"There are quite a few players that have been in the squad for a number of years that we know a lot about, so that's why there is a chance for some of the fringe players and younger players, and even more experienced players, to go out there on Saturday and perform," Gatland said.
"If you want to impress, then in front of 75,000 people with the roof closed at home, there is no better opportunity, so I am trying to give these players the best possible chance to go out and perform.
"We have pushed the players right to the limit, and they have responded magnificently.
"We know how hard we trained in preparation for 2011 (World Cup), and this has definitely been a step up. For everyone, it shows how much they want to make the World Cup squad and be a part of it, and it is going to be tough on us as coaches and selectors having to let some players down when we make that final cut.
"We haven't done a huge amount of contact stuff, but the forwards had a pretty tasty session this morning. They really ramped it up.
"There were a couple of little niggles and fights at training with the forwards. When they are holding and grabbing each other, you can tell there is a little bit of tension in the air. They are pretty aware of how important Saturday is, and the opportunity open to them."
There are two more uncapped players on the replacements' bench in New Zealand-born fly-half Gareth Anscombe, whose mother is from Cardiff, and Anscombe's Cardiff Blues colleague, hooker Kristian Dacey.
Had it not been for what Gatland described as "a slight thigh strain," it is likely that Anscombe would have started against Ireland this weekend. T he team will be captained by Scarlets centre Scott Williams, who leads his country for the first time.
Elsewhere in the line-up, there is only a second Test start at fly-half for Gloucester's James Hook since the 2011 World Cup, although his half-back partnership with Mike Phillips boasts a combined total of 170 caps.
And while the uncapped starting quartet have golden chances against Ireland to press their claims, the same applies to players like full-back Hallam Amos, prop Nicky Smith and number eight Dan Baker, who packs down in the back-row alongside Moriarty and Justin Tipuric.