Following his seventeen years in Italian Serie A, he served on the Board of Directors of Leeds United Football Club and helped contribute in July 2020 to the club’s historic promotion back to the Premier League following a 16 year hiatus in the English Football League Championship.

He immediately contributed his economic leadership by creating a new economic model for Italian Serie A clubs whereby U.S. Lecce has been recognized for their solution to “financial sustainability” - valorization of talent, balancing sheets returning to profit and self-sufficiency from shareholders soundly based on and organically working with the Sports Division.

[8] A chartered accountant and fiscal lawyer by profession, Mencucci joined ACF Fiorentina as CEO and board director in the summer of 2002 when the Della Valle Family, owners of the fashion brands Tod's, Fay, Hogan and Roger Vivier, acquired the defaulted club and initiated a new entity starting from the 4th tier Serie C2.

The club also qualified for the 2008–09 UEFA Champions League and again in 2009–10, where they were eliminated in the round of 16 by Bayern Munich, but recorded wins home and away, over Liverpool in the group stages.

[18][19] Mencucci implemented the Della Valle initiative and became the first Serie A club to financially sustain a non-profit association, Save the Children.

[20][21] Since 2007, Mencucci led all of ACF Fiorentina's international initiatives, which were first launched in the United States of America and were designed to identify young talented players and spread the expertise and culture of the club.

[26][27] In 2013, Fiorentina together with other Italian teams helped to form the Indian Super League (ISL) with aims to provide stimulus to the growth and development of football in the state of Maharashtra.