He was a surprise signing for the Catalans in 2019 as a stop-gap option in the January transfer window, and though he featured only five times, he was given a taste of what it is like to train alongside a player he believes to be the world’s greatest.
"While training with him, I felt inadequate for the first time in my career. He was doing incredible things. I felt like saying: 'I'm done, I'm going to quit playing!'"
Meanwhile, Boateng confessed that he thought there must have been some mistake when he heard that Barca were after him.
“At first, I didn't believe it. I thought it was Espanyol who wanted me, not the real Barcelona!” he said. “Those six months were incredible.”
Since leaving Camp Nou in the summer of 2019, Boateng has played with Fiorentina and Besiktas, while he now finds himself at Monza in Italy’s second tier.
Looking back on a career that has also seen him turn out with the likes of Tottenham, AC Milan and Dortmund, he has some regrets.
"When I was young, at Tottenham, it's true: I bought three luxury cars in one day, but there was so much pain inside me," he said. "I was trying to buy happiness. I wasn't happy. I wasn't playing. I wasn't well and so I was looking for something else. Sure, I would change that part of my past.
"Often, I trusted only my talent and, with the talent I have, without being arrogant, I could have done a lot more. Although, I have had a beautiful career anyway."
Monza, who are in the middle of the Serie B table, are being funded and run by former Milan supremos Silvio Berlusconi and Adriano Galliani.