Messi has taken over Barca's club captaincy from Iniesta after the veteran's departure to Japan.
Iniesta said, "I have a little advice for Messi. Although he did not wear the armband before, Leo always acted as captain.
"The captains have a very strong potential to manage a team, Messi is the captain of the Argentine team. The only thing I did was to appreciate him and for me he was the captain of FC Barcelona.
"For him, after so many years spent at the club, I guess it's a new experience."