Rakitic joined Barcelona in 2014 before he left Camp Nou to return to Sevilla ahead of the current season.
In an exclusive interview with Goal, the 33-year-old spoke about the pair's time together and his wish for Messi's future.
What was said?
"A player always wants to compete with and enjoy the best players and when it's the best of them all, it's even better," Rakitic said of Messi. "It was an incredible six years, you learn a lot of things.
"I look at Leo, who has gone nine seasons in a row scoring at least 30 goals, and it seems like a video game.
"If you do that on the Playstation, they'll tell you that you're messing with people and you know all the tricks. You simply have to enjoy it every day.
"I am proud to have spent so many years with him, to have fought for so many titles and to have won so many titles with him.
"Sincerely, if I've been able to help him, even a little bit, it's very special. It was very special to share a dressing room with so many great players at Barcelona."
Speculation over Messi's next move has been rife as the 33-year-old enters the final weeks of his contract with Barcelona.
Rakitic, though, is hopeful that Messi will choose to remain where he's been since the start of his professional career.
"I don't know [what he'll decide], I hope that he stays," Rakitic said. "Not just at Barcelona but here in Spain in La Liga. I believe that as fans we can say that the best for us is that he stays at Barca.
"As a friend and former team-mate, I wish the best for him and his family, and that he decides what he believes is best for him."