during the 2011–12 season, o'brien scored four goals in six-minutes and 10-seconds in a 7–4 win over the moncton wildcats. on april 5, 2012, o'brien signed an amateur tryout agreement with the st. john's icecaps of the american hockey league (ahl) but he returned to the acadie-bathurst titan for the 2012–13 season as an assistant captain after playing one game. during that season, o'brien broke his 186-game streak with no penalties in a 5–1 loss to the moncton wildcats. o'brien was the recipient of the chl player of the week for the first week of january for recording two hat tricks that week. he won the frank j. selke memorial trophy for the second time at the conclusion of the season, having only accrued two penalties that season.