I've said this whole time that he's an injury risk, but Granderson was also injured last year and saw a big drop off in power because of the location of the injury (forearm/wrist). Those injuries zap power just as much as Kemp's does. What you look at now, with both coming into 2014 healthy, is their talent level when healthy, and I don't think that is even close.
Saying that Kemp had an .834 OPS over the past 2 seasons is misleading given that 1. he had a .906 OPS in 2012 and 2. when he came back from his injury in September, he hit .314 with an .870 OPS.
Granderson, over the past 2 years, has posted a .788 OPS, and in neither year individually did he sniff an .834 OPS, much less a .906 OPS.