In 481 career NHL regular-season games, all with the Oilers, Gagner has accumulated 101 goals and 194 assists for 295 points, along with 244 penalty minutes.
Gagner, a native of London, Ontario, was originally drafted sixth-overall by the Oilers in the 2007 NHL Entry Draft.
Purcell, 28, appeared in 81 games for Tampa Bay last season, registering 12 goals and 30 assists for 42 points and 14 penalty minutes.
The St. John's, Newfoundland, native has spent time with the Los Angeles Kings and Tampa Bay Lightning. Purcell has accumulated 75 goals and 153 assists for 228 points and 66 penalty minutes in 401 career NHL games.