The only two things comparable between Darko and Luke arethey both weren't born in the States and that they are seven foot.
I get what Diz is on about. The centre position has changed heaps in the last 3 or 4 years. Forget the old plodding 7 foot stiff, only plays back to basket type of style (Luke's style). The only true old school centre still left is Shaq and Deke. The game was become so quick that teams can't really afford to have a plodding centre.
If Luke played against Chris Dudley, Cadillac Anderseon, Blair Rasmussen, Alla Abdelnaby, Randy Bruer, Bill Wennington, Dwayne Schnitzus and Brad Lohaus then he would be fine and hold his own. He can't and won't against the like of Amare and such.
Ten years ago being 7 foot got you a roster spot. Today it doesn't. Have a look at the mobility of players compared to 3 years ago, compared to 5 years ago, compared to 10 years ago. There are now PF's that are 7 foot. 10 years ago their wasn't one.