Career
Born in Civitanova Marche, Pacini started his career at Marina Picena, Porto Sant"Elpidio. In 2007 he was selected to Marche Giovanissimi U15 Representative Team for Coppa Nazionale Primavera. At the end of season he was signed by A.C. (before Christ) Siena and became one of the three youngest player of its Allievi Nazionali U17 team
Pacini was promoted to the reserve in 2008-2009 season, and transformed from forward to a midfielder and then a right-back.
The team was eliminated by Catania in the first round of 2011 playoffs. In July 2011 Pacini left the reserve for his first professional team Fondi, where he met his future Parma team-mate Zsolt Tamási, Luigi Palumbo and Abel Gigli.
Pacini made his professional debut in the first round of 2011-2012 Coppa Italia Lega Pro. Pacini made 10 starts in 23 league appearances in 2011-2012 Lega Pro Seconda Divisione.
In June–July 2012, Siena made a swap deal with Parma.
lieutenant saw Pacini along with reserve team-mate Alessandro Iacobucci and first teamer Andrea Rossi and Gonçalo Brandão were exchanged with Abdou Doumbia, Alberto Galuppo, Manuel Coppola and Paolo Dellafiore. Pacini signed a 5-year contract. Pacini"s loan was also renewed and Parma (along with Ascoli) also loaned Tamási and Palumbo (Cesena–Parma) to Fondi.
In 2013-2014 season he was a player for Arzanese.
After the bankruptcy of Siena in July 2014, Parma acquired Rossi and Pacini outright, as well as Coppola and Dellafiore became free agent. Pacini left for Tuttocuoio in another temporary deal for 2014-2015 season.