Reina has been allowed to leave Anfield temporarily after the Reds brought in Simon Mignolet from Sunderland this summer.
The player himself expressed his own surprise at the deal and accused Liverpool of going behind his back to arrange his switch to Italy, before later backtracking over his claims.
Benitez, who first brought Reina to Liverpool in 2005, says he had not expected the ‘keeper to be available and was planning on signing Queens Park Rangers goalkeeper Julio Cesar instead.
“Obviously I know the situation and I was surprised,” he said. “We were trying to sign Julio Cesar and it was a surprise for us when Pepe Reina was available.
“For us it is a big boost and it is really important because he is a great player so we are really pleased.
“He has a great relationship with the fans and the club so I don’t think he has any problem with them.”
When asked if Reina was still world class, Benitez said: “100% – he is still a fantastic ‘keeper.”