Salah was signed by Mourinho's Chelsea from Basel at the tender age of 21, after impressing as a youngster in the Swiss club.
His time at Stamford Bridge, however, failed to live up to expectations, as he received only fleeting first-team opportunities under the manager before leaving the club for Roma just over 18 months later in the summer of 2015.
Salah has since gone on to establish himself as one of the world's premier strikers, leading Liverpool to the Champions League final in 2017-18 and earning himself sixth place in the Ballon d'Or vote eventually won by Luka Modric.
But Mourinho believes it is unfair to accuse him of wasting the Egyptian's talents.
"First of all let’s start with Salah. Because lots of things have been told which are not true," he explained to BeIN Sports.
"For a start people try to identify me as the coach that sold Salah. I am the coach that bought Salah. It’s completely the wrong idea.
"I played against Basel in the Champions League. Salah was a kid at Basel. When I play against a certain team I analyse a team and players for quite a long time.
"And I fell in love with that kid. I bought the kid.
"I pushed the club to buy him and at the time we already had fantastic attacking players - Hazard, Willian, we had top talent there. But I told them to buy that kid. He was more a winger coming inside than a striker."
"He was just a lost kid in London. He was a lost kid in a new world," Mourinho added.
"We wanted to work him, to become better and better and better. But he was more of the idea of wanting to play and not wait.
"So we decided to put him on loan, in a culture I knew well. Italy. Tactical football. Physical football. A good place to play.
"Fiorentina are a good team to play for without the pressure of playing for the title. And we decided that move there.
"When the club decided to sell him it was not me. I bought him, I did not sell him."