Devils Trade Brian Rolston to Islanders for Trent Hunter

The New Jersey Devils traded Brian Rolston to the New York Islanders for Trent Hunter. It is unlikely that Hunter is going to get any better, and Rolston is the superior player. Why did the Devils trade a 2nd or 3rd line forward in exchange for a 4th line forward?

The Devils needed to clear up Rolston's cap space of $5,062,500 giving them a savings of $3 million to aid in signing their star forward Zach Parise. The Islanders on the other hand needed to reach the cap floor and hope Rolston can add veteran leadership to their crop of young players for the 2011-2012 NHL season.