I'd be interested to know where Ziegler ranked in your offensive efficiency stat. I don't know how to compute it, but I would have to think that Ziegler was one of the more inefficient offensive players in the country last year. He hoisted up 431 shots and took 194 free throws to average 15 points per game. While 46% from the floor is okay, he was only 29% from 3pt range and 49% from the FT line.
Short answer: His rank isn't impressive, but I think he'll continue improve.
Longer answer:
Like GV noted, his Offensive Rating (ORtg) was 95.x (depending on your source it can vary just a tiny bit, but it's all about the same) which was negatively affected by the things we've talked about in this thread. However, he does a lot of things well and is capable of producing a very good ORtg in the future (and I think he will, whether it's at CMU or elsewhere).
The ORtg measures personal offensive efficiency. While it's a precise measurement, taking two players and simply comparing their ORtg doesn't necessarily tell you much.
Going a little bit deeper (see
www.crackedsidewalks.com for an explanation of Offensive Value Add), Zeigler did add a little bit of offensive value although not much. This measurement is far more complex than a personal efficiency calculation, but I think far more telling. A key thing to remember (and it's important when looking at a team like Minnesota and its players) is that players who both (a) are more involved in the offense and (b) play more can generate more value to the team.
Zeigler played almost 4 of every 5 minutes and was used in 31.6% of his team's possession. That is significant.
Not to get into this too much here, but when I look at the potential of teams in the future, one thing I try to do is look at which players I think are capable of adding significant value. ORtg is certainly important, but you also must consider how involved in the offense the player will be and how much they'll play. (and if a guy is going to be called on to do more, what will that do to his ORtg?.. diminishing returns, forcing, etc.)