The Atlético Madrid forward, whose two-year spell at Old Trafford ended with a move to Villarreal in 2004, became a cult figure at United despite his unimpressive record of just 17 goals in 95 appearances.
Having arrived from Independiente for £6.9 million in January 2002, the Uruguayan took 27 games to score his first goal for the club.
A double strike in a 2-1 victory at Liverpool in 2002 cemented his popularity amongst the United supporters, but Forlán admits that his time was up at Old Trafford after he defied Ferguson over his choice of footwear.
Forlán, who is set return to England when Atlético face Chelsea in the Champions league group stages on Oct 21, said: "Ferguson wanted me to play with high studs, the interchangeable ones that suit wet pitches, but I feel more comfortable in low ones.
"I agreed to change, but I didn't and, against Chelsea, I slipped in front of goal and wasted a chance.
"Afterwards, I rushed to the dressing room to change boots, but Ferguson caught me. He grabbed the boots and threw them. That was my last game for United."
Forlán has since made a huge success of his career in Spain, twice winning the European Golden Boot as the continent's leading goalscorer.
And he admits that he has now buried the hatchet with Ferguson, who even asks his advice on possible South American signings.
Forlán said: "When we were in London (with Villarreal before a Champions League game against Arsenal) Ferguson showed upá at our hotel.
"I still have a good relationship with Sir Alex and his brother Martin. "We have conversations and sometimes he asks me about South American players I might know of."