The downfall of P.K. Subban has really begun during his last year in Nashville. He was nominated for the Norris Trophy just the year before, but the next campaign wasn't what people would have expected.
Therefore, he was traded to New Jersey, and things continued to go poorly. He only registered 37 points in 112 games. This season, his offensive production has picked up a bit, but his overall game is not good.
And with a salary of 9M$ per year, we can understand why the Devils aren't too keen to agree on an extension with him. That's why the team management told Subban that he could be traded from here to the deadline.
With that being said, at a reasonable amount and in the good spot, Subban could be valuable to a team. Don't forget that he's only 32 years old...