While Steimsma brings great energy, and is a talented shot blocker, he still has a ways to go. I also think his shot blocking will take a hit as teams start to get more of a book on him. He has gotten a lot of blocks on perimeter shots where guys will be pumpfaking in a couple weeks. Also, he has not done a good job boxing guys out, and has not been great defending guys one on one, particularly in the high post (he has been beaten off the dribble a handful of times).
With that said, he has given them energy that they desperately needed, and at the very least should give this years C's what last years team got from Erden...and that is invaluable.
Ultimately, I would be shocked if he is playing significant minutes come playoff time though.