Fly-half Stephen Jones has given Wales an injury scare after complaining of more calf problems before Saturday's final World Cup warm-up with Argentina.
Jones had been due to start on the bench at the Millennium Stadium, and would have won a record 101st cap.
But Wales have erred on the side of caution and replaced the 33-year-old with Scarlets team-mate Scott Williams.
The same calf injury forced Jones to drop out of the side to face England in the first warm-up match in Twickenham.
Martyn Williams captains the side as another late injury-enforced change saw number eight Ryan Jones relinquishing his place.
Wales name their 30-man Cup party on Monday and Williams has been recalled to lead the team for the first time since November 2010.
Wales assistant coach Howley says the veteran flanker must help ensure Wales play at high-tempo against the Pumas.
"That's when you see Martyn Williams involved in the game," said Howley.
Howley did little to dispel Williams' thoughts, saying: "We want him to be a link I think its' really important... when you play against Argentina the tendency is [to have] a very stagnated game.
"We want to create a tempo, play with an intensity and obviously keep the ball in hand.
"And we need to get a link between the forwards and the backs and Martyn is crucial to that role and he has been for many, many seasons.
"When Martyn plays the game when the intensity and tempo is up, that's when you see Martyn Williams involved in the game and we just have to make sure that the game is like that."
Howley also says the emergence of youthful back-row talents Justin Tipuric, Sam Warburton, Danny Lydiate and Toby Faletau has brought the best out of Williams and Ryan Jones in summer training.
"Ryan Jones was absolutely outstanding and Martyn Williams likewise [in Wales' training camps]," said Howley.
"They're old heads, they've been around the block a few times and they know what international rugby is about."
Williams returns after coming on as a replacement against New Zealand in November and having been overlooked for the Six Nations.
That came seven days after Warren Gatland's men lost 23-19 at Twickenham in the first of three warm-up games.
Gatland will announce Wales' 30-man squad for the World Cup on Monday 22 August, two days after the Argentina match.
Williams' opportunities with Wales have been limited due to the emergence of Cardiff Blues team-mate Sam Warburton.
Warburton has captained Wales in previous three matches due to the absence of regular skipper Matthew Rees, who will miss the World Cup due to injury.
Wales face South Africa in their opening pool game on Sunday, 11 September in Wellington.
Wales: L Byrne (Clermont Auvergne); L Halfpenny (Cardiff Blues), J Davies (Scarlets), J Roberts (Cardiff Blues), G North (Scarlets); J Hook (Perpignan), T Knoyle (Scarlets); P James (Ospreys), R Hibbard (Ospreys), A Jones (Ospreys), B Davies (Cardiff Blues), A-W Jones (Ospreys), D Lydiate (Newport Gwent Dragons), M Williams (Cardiff Blues, capt), A Powell (Sale).
Replacements: H Bennett (Ospreys), R Bevington (Ospreys), J Thomas (Ospreys), J Tipuric (Ospreys), L Williams (Cardiff Blues), S Williams (Scarlets), A Brew (Newport Gwent Dragons).
Argentina: Martin Rodriguez; Horacio Agulla, Marcelo Bosch, Santiago Fernandez, Gonzalo Camacho; Felipe Contepomi (capt), Nicolas Vergallo; Rodrigo Roncero, Mario Ledesma, Juan Figallo, Manuel Carizza, Patricio Albacete, Julio Farias Cabello, Juan Manuel Leguizamon, Juan Fernandez Lobbe.
Replacements: Agustin Creevy, Martin Scelzo, Mariano Galarza, Alejandro Campos, Alfredo Lalanne, Nicolas Sanchez, Juan Imhoff.