He has done really well since coming in. His mobility is the clincher for me . He can afford to play the DMC role 5-10 yards further forward than the other options in his position which inturn let's us get forward faster and doesn't invite the opposition on to our defence as much as Jedinak and Whelan. Also with his back to goal with two men around him he is far better than Jedinak at getting the ball out from under his feet and getting the pass away. Jedinak and Whelan have both been caught in possession far too much.
Edit: thinking about it . It seems to basically be age that is catching out both Whelan and Jedinak. Just both seems a fraction slow to move the ball. Signals not getting from brain to feet as fast anymore. All in my opinion of course.