Jerome Boateng called Jose Mourinho as the Bayern Munich defender rejected the overtures of Manchester United as well as Paris St Germain over the summer.
The Red Devils boss had been desperate to reinforce his backline in the transfer window, with the 30-year-old among the players targeted.
United had been keen to bring Boateng on loan rather than the permanent deal Bayern Munich had been looking for.
The Old Trafford giants had misgivings over his fitness, but the Germany international nipped any interest in the bud during a conversation with Mourinho.
"I had enquiries from Paris St Germain and Manchester United, and I considered them," he said.
"Not because I wanted to leave Bayern Munich by all means. It was no escape, but rather the thrill of a new challenge.
"I feel completely content at Bayern, one of the biggest clubs in the world."
He added: "I phoned Jose Mourinho and told him that his interest honoured me and thanked him that he put his back into United for me.
"I explained to him my reasons for not joining.
"It's difficult to leave FC Bayern. Everything has to fall in place to top this club, if I do it."