Cardiff centre Cory Allen has been handed his first Wales cap for their Test clash with Argentina at the Millennium Stadium on Saturday.
Allen, with only 10 senior appearances to his name, replaces an injured Jonathan Davies alongside Scott Williams in midfield, while at the other end of the spectrum prop Gethin Jenkins will make his 100th Test appearance.
The youngster's inclusion is one of four changes from the side beaten by South Africa last weekend, with Dan Biggar coming in at fly-half in place of Rhys Priestland.
Scarlets youngster Rhodri Jones replaces Adam Jones, who has a calf injury, opposite Jenkins in the front-row and the final change means a shuffle in the back-row with Dan Lydiate sidelined by ankle trouble.
His absence means a place for Justin Tipuric at No 7 with skipper Sam Warburton moving to the blindside.
"Last weekend will stand us in good stead in terms of physicality and intensity as Saturday will be a huge battle against Argentina," Gatland said.
"They will be looking for a repeat of last year (Argentina beat Wales 26-12) and we will need to be more clinical to get the result we are aiming for.
"We have been working hard to ensure we convert the chances we create and encourage the players to look for, and exploit, opportunities and space.
"Saturday will be a huge occasion for Gethin, and a fantastic milestone.
"We have made a number of changes due to injury, but it's a great opportunity for players we have been very impressed with.
"For Cory, it will be his first taste of international rugby and for Rhodri a chance to gain more experience. Justin played very well off the bench last weekend, and Dan's injury gives him the chance to start the game."
Argentina make four changes from the side beaten by England last weekend with winger Santiago Cordero making his first Test start after coming off the bench at Twickenham.
Scrum-half Martin Landajo replaces Tomas Cubelli and Joaquin Tuculet plays at full-back in place of Lucas Gonzalez Amorosino, with Manuel Carizza coming in at lock for Mariano Galarza in the only change to the Pumas pack.
Wales: L Halfpenny, G North, C Allen, S Williams, L Williams, D Biggar, M Phillips; G Jenkins, R Hibbard, Rhodri Jones, B Davies, A-W Jones, S Warburton (capt), J Tipuric, T Faletau.
Replacements: K Owens, P James, S Lee, L Charteris, Ryan Jones, L Williams, J Hook, A Beck.
Argentina: J Tuculet, H Agulla, M Bosch, S Fernandez, S Cordero, N Sanchez, M Landajo; M Ayerza, E Guinazu, M Bustos, M Carizza, P Albacete, P Matera, J F Cabello, J M Leguizamon (capt).
Replacements: S Iglesias, N Lobo, M Diaz, T Lavanini, L Senatore, T Cubelli, G Azcarate, L G Amorosino.