Cowen, 26, has appeared in 249 career NHL games, all with the Ottawa Senators, tallying 46 points (15 goals, 31 assists). The 6-foot-5, 238 -pound rear guard was selected by Ottawa as the ninth overall pick in the first round of the 2009 NHL Entry Draft. He dressed in all 82 games for the Sens as a rookie in 2011-12-the only NHL rookie defenseman to appear in every game-and notched 17 points (5g/12a). Two seasons later, Cowen racked up 15 points, including a career-high six goals, in 68 games during the 2013-14 campaign.

He was acquired by Toronto late in the 2015-16 season (Feb. 9, 2016) but did not appear in a game with the Maple Leafs, and did not play in 2016-17. Cowen has also seen action in 17 career NHL playoff contests, picking up four assists (0g/4a).

The Saskatoon, Saskatchewan, native played junior hockey for the Spokane Chiefs, where he won a Memorial Cup in 2008, was named to the WHL West Second All-Star Team in 2009-10 and WHL West First All-Star Team in 2010-11.