Gudbranson, 27, joined the Penguins via trade in February, acquired in exchange for forward Tanner Pearson — who, in turn, was acquired from Los Angeles for forward Carl Hagelin in 2018.
The Ottawa-born defenceman suited up for 26 games with the Penguins in total, posting two points while skating an average of 17:56 minutes between last season and this one. He also logged three years with the Vancouver Canucks and five years with the Florida Panthers, who drafted him third overall back in 2010.
Martinsen, 29, split the 2018-19 season between the Chicago Blackhawks and AHL Rockford, posting four points in the big leagues and 11 in the minors. The Baerum, Norway native has also spent time with the Montreal Canadiens and Colorado Avalanche organizations, and played one game for AHL San Diego this season.