Christensen appeared in 20 games for the Rangers this season and has compiled a goal with four assists for five points. He notched 11 goals and 27 points in 63 games for New York last season.
The 28-year-old veteran has 62 goals and 94 assists for 156 points in 358 games during seven seasons with Pittsburgh, Atlanta, Anaheim and the Rangers.
Wellman notched two goals and five assists in 14 games for Minnesota this season. He also accumulated 13 goals and 24 points in 25 games at the Wild's AHL affiliate in Houston.