The Gunners signed the defender from St Etienne before the start of the season, though agreed to loan him back to ASSE for this campaign.
Campbell, now Southend United manager, told Le Talk Show Stéphanois: "We made a very clever signing last summer with Saliba.
"(Mikel) Arteta is not an idiot, he knows he has to adjust his back line if he wants to get back in the game to win titles. Saliba has been good this season but he is still very young and needs a leader next to him to help him develop.
"He will help next season, but he still needs a partner for sure. The club must still add a world class leader to this back line if they want to return to the game to win titles."