Ronaldinho joined Barcelona in 2003 and inherited the iconic number from Argentine midfielder Juan Roman Riquelme - who was sent on loan to Villarreal for two seasons.
The Brazilian star left after six years with the club, scoring almost 100 goals in just over 200 appearances.
And Messi has revealed in an interview with Barca TV that Ronaldinho promised him the No.10 shirt months before he announced he was leaving.
"Before leaving the club [Ronaldinho] was coming off a few months where he was thinking about things," Messi said.
"He had it in his mind that he was leaving and he told me to have his number. I took it without looking at what he had done with the shirt. If I did, I would not have taken it."
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Messi has won 21 trophies with the No.10 on the back of his Barca jersey, and a total of 26 with the Spanish giants, and the four-time Ballon d'Or winner has now praised his former team-mate for his welcoming nature when he broke into the first-team squad.
"Everyone welcomed me into the dressing room, and [Ronaldinho] welcomed me in a spectacular way," he said.
"To go into that dressing room was not easy but he made it all so much easier. I was very comfortable by not only Ronnie's welcoming but everyone.
"Those who came up from the [Barca] B sat on the other side [to the main group]. The locker room did a 'U' and we sat in-front, and there came a moment that [Ronaldinho] told me to go to his side and that I no longer needed to be where I was anymore.
"There was a spot free and there was Deco and [Thiago] Motta right there, and he sat me right beside them. I must admit at the start it was hard.
"But he said no, that I was good where I was until I basically obliged to sit there."
Ronaldinho was just as complimentary of his former team-mate.
"He's a simple person, very chilled, and he sat by my side in the dressing room," he said. "We had the chance to start a good and honest friendship. He's a great man."