Djokovic was trying to win the match without moving very much. Hopefully it's just him being lazy. He did not have the top gear hitting but kept trying to end points quickly and lunge to shots he need to run to . He wanted to win this match with minimal effort but of course Tomic would want to give everything in front of the Perth crowd, no half assed performance like against Roddick.
Actually it was very Murray like from Djokovic. Luckily this is a expo and not a Masters where you see this sort of thing send Murray out early.