The 25-year-old stated that the likes of Cesc Fabregas and Gerard Pique used to think he could not speak in his younger days, and also thanked Neymar for his recent comments
The Barca forward scored a record 73 goals in 60 appearances in a stellar 2011-12 season as the club won four trophies, but his ability on the pitch was questioned early on in his career by his teammates.
"Cesc Fabregas told me that when I was little, I dressed in silence and they thought I was dumb," the 25-year-old told Hungarian magazine Kepes Sport.
"Now I am more open, and not so shy in the locker room as it was before in La Masia."
The Argentine international, who admitted that he did not watch any Euro 2012 matches, also revealed his pleasure at recent comments made by Brazilian wonderkid Neymar, who labelled the Barcelona forward as "the best in the world".
"I am very grateful for the comments of Neymar about me. It is always nice when it comes from another player," he continued.
Messi will start pre-season training with the Blaugranaon Monday, ahead of the first friendly against Hamburg on July 24.