Mancari was called up from Portland on November 21, 2008.[2] The next day, he scored his first NHL goal against the New York Islanders. He was reassigned to the AHL on December 7, 2008, and named to the 2009 AHL Canadian All-Star team on January 6, 2009.[3]
Mancari began the 2010–11 NHL season in Portland where he played 23 games for the Pirates before being recalled to the NHL to suit up for the Sabres on December 7, 2010. Mancari assisted on one goal in the away game against the Boston Bruins.[4]
He signed a one-year contract worth $525,000 with the Vancouver Canucks on July 1, 2011.[5] After one season in the Canucks' organization he returned to the Sabres, signing a one-year contract.[6]
On July 5, 2013, Mancari again left the Sabres organization and signed a one-year, two-way deal with the St. Louis Blues.[7]
On March 9, 2016, Mancari left Augsburger as a free agent and signed a two-year deal with fellow DEL side Krefeld Pinguine.[10] In leaving Krefeld after just one season, Mancari continued in Germany by appearing in the DEL2 with EHC Freiburg.
On May 9, 2018, Mancari left Germany to sign a one-year contract with the Graz 99ers in the neighbouring EBEL.[11] Before joining the 99ers for pre-season, Mancari was unable to partake in a physical, cancelling his contract with the club.[12] He later opted to return to EHC Freiburg on December 13, 2018.[13] After playing in 10 games with Freiburg, Mancari retired from professional hockey on January 13, 2019.[14]