O'Brien, 23, played in three games for the Capitals this season, after making his season debut on Nov. 4 at Boston. O'Brien registered two points (one goal, one assist) and 28 penalty minutes in 17 career games with the Capitals. The 6'1", 215-pound forward made his NHL debut on Oct. 9, 2014 against Montreal, earned his first NHL point with an assist on Oct. 14, 2014 against San Jose and scored his first career NHL goal on Oct. 26, 2014 at Vancouver.
In nine games with Hershey this season, O'Brien, 23, has two goals and four penalty minutes. Last season, O'Brien recorded 30 points (10g, 20a) in 64 games with Hershey and ranked third on the team in penalty minutes (117), seventh in assists and ninth in points. O'Brien recorded a career-high three points (2g, 1a) on Dec. 30, 2016 against Bridgeport and registered seven multi-point games last season. The Halifax, Nova Scotia, native has earned 56 points (23g, 33a) in 177 career AHL games with Hershey.
O'Brien signed with Washington as a free agent on Oct. 6, 2014.
