1. Diego Fabbrini previously played for Empoli, where his career began, Udinese, Watford, Birmingham City, Botosani, CSKA Sofia, Dinamo Bucuresti, Ascoli and Lucchese, with loan spells at Palermo, Siena, Millwall, Middlesbrough, Spezia, Oviedo and Alessandria.
However, towards the end of the season, Diego Fabbrini soon have his playing time at Palermo reduced and finished the season, making 8 appearances and scoring once for the side.
On 19 July 2013, Diego Fabbrini was one of seven Udinese players to join Watford on permanent deals; he signed a contract until 2017.
However, despite making an impression for the side, Diego Fabbrini found himself behind the pecking order in the first team.
An unused substitute for Birmingham's next match, Diego Fabbrini was expected to start in the visit to AFC Bournemouth three days later, but broke his nose in training.
Diego Fabbrini added two more goals against Oldham Athletic and Sheffield Wednesday.
Diego Fabbrini signed a three-and-a-half-year contract with Championship club Birmingham City on 27 January 2016.
Diego Fabbrini made his second debut three days later, as a 62nd-minute substitute in a goalless draw away to Bristol City.
Diego Fabbrini played regularly, making 17 appearances and scoring once as Spezia reached the play-offs.
Spezia did not take up their option, and Diego Fabbrini began pre-season training with Birmingham.
Diego Fabbrini was not in Birmingham's plans for the coming season, and at the end of the transfer window, in September 2018, his contract was cancelled by mutual consent so that he could join Romanian Liga I club FC Botosani.
On 28 May 2019, CSKA Sofia announced that Diego Fabbrini signed a three-year contract with the club.
Diego Fabbrini spent the second half of the season on loan to another second-tier club, Alessandria, but the team were relegated and they did not take up their option to buy.
On 31 January 2023, Diego Fabbrini signed with Serie C club Lucchese until the end of the season.
Diego Fabbrini made his debut for the Italy U-21 side on 3 September 2010 in a qualification match against Bosnia and Herzegovina played in Sarajevo.
Diego Fabbrini scored his first goal for the U-21s on 24 March 2011, in a friendly against Sweden.
Diego Fabbrini went on to make 12 appearances and scoring once for the U21 side.
Diego Fabbrini was called up to the senior squad for a friendly on 15 August 2012 against England, to replace Mario Balotelli who had withdrawn at short notice through illness.