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.
After being through it and seeing the other [outdoor] games on TV, just the atmosphere is spectacular. To stand here -- and we are essentially almost on the blue line -- and look up [into the stands] and knowing it is going to be packed and playing our biggest rival in this setting is going to be pretty special.
— Bruins president Cam Neely on the 2016 Bridgestone NHL Winter Classic between Boston and Montreal at Gillette Stadium on
Jan. 1, 2016