Born in Chiavenna, Lombardy, Pasini started his career at A.C. Milan. From 2008 to 2011 Pasini was a member of the reserve. On 20 July 2011 Pasini was exchanged with Matteo Chinellato in co-ownership in 3-year contract, (50% Chinellato €1.75M and Pasini €1.65M) and which Milan registered a capital gains of €3.3 million, however it was in terms of Chinellato's asset value of €3.5 million and vice versa (Genoa capital gains of €3.5M) . Furthermore, both clubs had to amortize the contract value (transfer fee) as the cost of hiring the player in installments, as well as VAT. He signed a 3-year contract. On 27 July 2011 Pasini left for Carrarese in temporary deal. He made 17 starts and 1 substitute appearance, mainly as a centre-back. On 1 June 2012, Milan acquired Chinellato and Pelé outright; Genoa acquired Pasini and Mario Sampirisi outright in the same deal, all in pure player swap as Pelé's price was €50,000 less.
In July 2012 he joined Serie B club Spezia Calcio in another temporary deal. He was signed by Venezia on 2 August 2013. Circa 2013 he also signed a contract extension which last until 30 June 2015.
Pasini played for Italy U17 team in 2008 UEFA European Under-17 Football Championship qualification (2 starts). He was the member of the squad for 2008 Minsk youth tournament. However no lineup was known. Pasini received call-up to Italy national under-18 football team in October 2008. However Pasini did not play any game for the U18 in 2008–09 season nor U19 in 2009–10 season. He received a call-up for a friendly match in October 2009. Pasini played once for the U20 team in 2010–11 Four Nations Tournament.