Casey Jay Wellman was born on October 18, 1987 in Castro Valley, California. A product of the Cedar Rapids Rough Riders of the USHL, Wellman also played collegiately for the University of Massachusetts Amherst. On March 16, 2010, Wellman signed as a free agent with the Minnesota Wild.
During the 2009-10 season, Wellman made his professional debut for the Wild. In total, he would appear in 12 games for the club and record four points.
On February 3, 2012, Wellman's time in the Wild organization would come to an end. He was traded to the New York Rangers in exchange for Erik Christensen.