There were also some poignant recollections from Pochettino about a player who he discovered in the depths of despair when he joined the club in the summer of 2014, but went on to become a mainstay of the Tottenham midfield, and an England global.
Mason started training with the club again in May a year ago but no expected return date was ever given and then Tigers boss Leonid Slutsky said in August that "the question is not just about football but about his life" when the player went to see a third specialist.
Hull manager Nigel Adkins added: "The injury happened before my time, but all I know is that Ryan has worked so hard in the time that I have been here".
"It is very sad news but he opens a door for his future with his family", Pochettino said after the draw with Juventus. '(The doctor) said there was a moment shortly after I arrived at the hospital, I think maybe just after I'd had a CT scan, that I was what they call "unresponsive".
"You see him on the training ground, he's done everything". He is 26 but he is an unbelievable person and has an incredible football brain.
"I've sought about ten specialists' advice, but the risk was too high". He was a very successful player, and he will be a very successful person with everything he wants to do.
Chelsea later tweeted: "Everybody at Chelsea Football Club sends our best wishes to Ryan Mason following his retirement". He was talking a lot with us, the coaching staff and [academy manager] John McDermott. "We wish him well and he's always welcome here".
"Don't worry Ryan because you are going to be a successful person in football outside of the pitch, no doubt about that".