Dewi Lake has replaced Jac Morgan as captain among 13 changes Wales have made for their second Rugby World Cup match against Portugal.
Lake comes in at hooker for Ryan Elias, with Louis Rees-Zammit and Taulupe Faletau the only surviving players from the team that beat Fiji in Sunday's thriller.
“We got the win (against Fiji), which was the main thing, but there is a lot to improve,” Rees-Zammit said.
“We've got Portugal next and we know they have got great backs, so it's going to be a tough game.
“We have got a game by game mentality, and that is our focus. You can't slip up.
“We respect Portugal. We know they have got some great backs, so we are going to have to train hard this week and get the job done.”
Elsewhere in the side, scrum-half Tomos Williams wins his 50th cap and centre Mason Grady gets his first World Cup start, along with Exeter second row pair Dafydd Jenkins and Christ Tshiunza who also play their first games in the tournament.
Williams pairs up with Gareth Anscombe in the half-backs, with the fly-half returning from injury in his first game for Wales this calendar year and making his first World Cup appearance since 2015, having previously been ruled out of the 2019 campaign.
Like Anscombe, captain Lake has had his preparation for the tournament disrupted by injury, but he packs down in an all-new front row alongside Dillon Lewis and Nicky Smith.
While Faletau is joined in the back row by Dan Lydiate and Tommy Reffell, and Johnny Williams lines up alongside Grady in the centres.
On the opposite wing to Rees-Zammit is Rio Dyer, with Leigh Halfpenny completing the back three and in the process becomes the oldest back in history to feature for Wales at a World Cup.
Wales boss Warren Gatland, taking charge of his 21st World Cup game as coach of Wales, said: “We've made a few changes this week given the six day turnaround.
“This is an opportunity now for this match day 23. I've said before, but there's some great competition within the squad which is what we want to see. There's a chance now for this group to go out Saturday and to put down their own marker in the tournament.
“We've done a thorough debrief of last week's game and know the areas we need to improve. We have a clear plan of how we want to play on Saturday and it's about going out there and executing that as we have prepared.
“Portugal are a skillful side and will be raring to go this weekend in their first match of the tournament. We're excited to get back out there and looking forward to seeing more great support from the travelling fans out in Nice.”
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