Wales great JPR Williams says James Hook should stand his ground and refuse to play at full-back.
Hook, 26, has played at number 15 in Wales's opening two World Cup games but has always voiced his preference to play at fly-half or centre.
And Williams said: "It's a different ball-game attacking from full-back than it is from midfield. I think he's a 10 or 12 - I always have done.
"If I was him I would stand up and say, 'I'm not going to play full-back'."
Leigh Halfpenny filled in at full-back and his break after catching a high ball created the decisive try.
Williams believes Halfpenny, who normally operates on the wing, should retain the number 15 jersey for the rest of the tournament, despite the availability of specialist full-back Lee Byrne.
"Byrne hasn't played well over the last two seasons," added Williams, who is widely regarded as Wales' greatest full-back.
"It's hard to believe that two years ago he was one of the best full-backs in the world. He hasn't shown that form for a couple of years.
"I thought Leigh Halfpenny played very well and effectively won the game against Samoa.
"The one thing I do know is the one thing the Welsh selectors don't seem to - that James Hook is not a full-back. I think everybody in Wales will tell you that.
"He's not comfortable under the high ball, he's out of position. It's a very difficult position and you can be exposed very easily.
"I'm very surprised that [Wales] keep picking him at full-back."
Williams feels Wales have an obvious place for Hook in midfield, where his "creativity" is needed to compliment the power of Jamie Roberts.
Another change advocated by Williams for the next game against Namibia would be to drop Mike Phillips in favour of Tavis Knoyle at scrum-half.
The former 1971 and 1974 Lions star said: "Mike Phillips is still very slow in getting the ball out.
"I think we've got to play the game at pace - that's why we lost against South Africa. In the last 20 minutes, we should have made changes and brought on some fresh legs.
"Knoyle should have been there to get the ball out wide because South Africa were out on their feet.
"We are better when we move the ball."