 With his NHL opportunities exhausted, O'Brien remained a free agent over the summer and into the 2016–17 season.On January 10, 2017, O'Brien opted to sign his first contract abroad, agreeing to an initial two-week contract that would extend for the remainder of the season with Finnish club, HPK of the Liiga.Midway into the following 2017–18 season, O'Brien was signed to strengthen the blueline of Austrian club, EHC Black Wings Linz of the EBEL, on November 9, 2017.