Valdes was confirmed as a United player on Thursday night and will provide more experienced and arguably more solid back-up to David de Gea than Anders Lindegaard.
With Lindegaard set to leave, Valdes’ arrival means United’s goalkeepers are as strong anyone in the league and Carragher believes it’s a good signing but de Gea will remain No.1.
“It’s an interesting deal and normally you don’t see two top ‘keepers at one club,” said Carragher.
“Valdes has had a great career at Barcelona, and Louis van Gaal obviously wants a better No 2 than what he’s got in (Anders) Lindegaard, and he’s gone for him, but there would be no doubt that (David) de Gea will be No 1 goalkeeper.”
But the former defender says United and van Gaal need to be set on a number one at the club and avoid a repeat of the constant change of goalkeeper that Sir Alex Ferguson tested between de Gea and Lindegaard at the start of the 2012/13 season.
“For outfield players’ psychology, they need to know who’s No 1, it gives them confidence. With (outfield) players you need competition and goalkeepers need competition as well, but you need knowledge of who is No 1. I think psychology with goalkeepers is a problem at times. We had Reina and Dudek, two top class ‘keepers and one had just won the Champions League, but we all knew Pepe was the No 1.”