I'm not a huge fan of PER, but I do like win shares and especially WS48 as a single-number, quick-and-dirty stat for rough comparisons. By that number, Perkins at 0.036 WS48 is having the worst year of his career. He's having a career year in free throw percentage, but his eFG% is at a career low, his rebounding percentage is at a career low, and it looks like he probably won't recover to blocking shots as well as he did pre-injury.
If you thought that Perkins was unlikely to get better and likely to get worse, with a possible career trajectory and aging pattern similar to Jamaal Magloire, would you be happy with his contract?