Of course McCarthy and Kersten were played with a fair degree of future about it. Really, if you're in a stated rebuild phase you're nuts if there isn't a heap of future about your decision making. Plus both were newbies to the setup, it's sensible to make allowances for adjusting.
You're not always going to get big stats playing in the forward line of course. Neverheless, Kersten got dropped twice, but he is a different type of forward than Taberner. Much faster, more capacity to fulfill a pressure forward role. He wasn't always successful at it, but he had less history than Taberner and more to find out. I reckon they were also wanting to see Taberner get more fierceness in his game.
All of which meant Kersten was played more than Taberner in 2017. This may change quite a bit as 2018 rolls on.