Both Pronger and Niedermayer have been part of the rumor mill for the last few weeks because Anaheim has been nowhere all season and is barely hanging in the Western Conference playoff race. Meanwhile Ducks GM Bob Murray said last week he is already thinking about next year, which was another way of telling his colleagues to start their engines because the race for one of former Norris Trophy winning defensemen was under way.
Whitney is one of the NHL's better young offensive defensemen, although he has struggled since returning from surgery that cost him the first half of the season. But he's signed for four more seasons at around $4 million per, which means Anaheim is looking at him to be part of the rebuilding process long after the two aging big guys are gone. In other words, Whitney is an insurance policy that gives the Ducks the latitude to to trade one of their valuable defensemen. The only question is which one.
Pronger has one season left on his contract while Niedermayer becomes a free agent in July and may very well retire, so you can debate about which one might be worth more leading to the deadline. But the Ducks would probably be better off trying to move Niedermayer as a rental -- the New Jersey Devils are thought to be very interested in bringing him back -- and keeping Pronger along side Whitney next season at least until the trade deadline. Either way, the Ducks have positioned themselves well.