The former France international believes Tito Vilanova's side would not be the same force without its influential midfielder
The Spain midfielder finished in second and third place behind the Argentine in the race for the Ballon d'Or in 2010 and 2013, respectively.
And while both players have played influential roles in firing the Blaugrana to the top of La Liga this season, Pires has singled out Iniesta for special praise.
"For me, Iniesta is the best player at Barca," Pires told La Xarxa Radio. "We always talk about Messi, but without Iniesta Barcelona are a different team.
"He is the master of the team. He is the one who sets the pace for the whole team. He plays very easy."
The former France international also spoke kindly of former teammate Cesc Fabregas, who has been in fine form at Camp Nou after a difficult start to the season.
"For me, the success of Cesc has been no surprise. He is doing every well and is a fixture in the side, and has been scoring a few goals."