Costello, 23, has 19 points (11 goals, eight assists) and 69 penalty minutes in 34 games as team captain with Notre Dame this season. He was originally selected by Ottawa with the 146th overall pick in the 2009 NHL Entry Draft.
Mullen, 27, has 20 points (7-13) in 46 games this season with Utica of the American Hockey League.
I downplayed the first one because I thought it's just a hockey game. We just want to win the game; it's against our rival and we want the two points. I downplayed it, but now having gone through the first one I look back and say, 'Geez, that was really cool.' I think as I've grown a bit older I've got a lot more appreciation for what we're allowed to do every day.
— Capitals forward Brooks Laich on the 2015 NHL Bridgestone Winter Classic, the second one of his career after 2011 in Pittsburgh