Zeller is basically Brian Scalabrine. He is just good enough to be on an NBA team and contribute as a big. They are good for the locker room. They are what Gerald Wallace was becoming as he adjusted to being a bench player but was simply out of gas.
He serves the Brandon Bass role. They are good guys who won't make waves. They might even help you win some games if forced to go with them.
I feel you're selling Bass short there in a big way. Sure he was never a star or a big name player, but he made some really big contributions to this team - not only in the regular season, but in the playoffs as well. Even playing alongside the likes of Rondo, Pierce and Garnett, bass still always managed to find ways to stand out from time to time.
He was a really hard working guy who improved ever year he was on the roster, and who contributed on both ends of the court. I see him as our "Tony Allen" type over that stretch - a guy who wasn't flash or a stat sheet stuffer, but just did a lot to help our success.
Given a choice between the current version of Sully or Bass from 3-4 years ago, I would take Bass in a heartbeat. At least with Bass there were two things you always knew you would get from him - effort and consistency.
You knew you could count on Bass every night to give you 12-15 efficient points along with 5-8 rebounds and some tough defensive effort. I would give my right testicle (not really, but you get my drift) if we could EVER get all of those things from Sully on a consistent basis.
As for Zeller, he's not so bad. Since he became a Celtic he's put up consistently strong Per-36 numbers (around 17 points, 9 rebounds, 2 assists, 1 block, 52% FG).
He's also fairly mobile for a 7-footer, he's been effective at the line (32.5% career Free Throw Rate, 78% FT) and he's shot nice career percentages from everywhere inside the three point line, as can be seen below:
0-2 feet: 63.3%
3-9 feet: 40.4%
10-15 feet: 41.7%
> 16 feet: 40.1%
In fact in that regard, offensively, Zeller is a lot like Al Horford before he added the three point shot. I say that because like Horford he's not much of a shot creator, but if you can get him open looks from pretty much anywhere inside the three point line, he's a knock down shooter and can make them all day lone.
The downsides are that he's a below average rebounder and he's a below average defender...but you could the same about Jahlil Okafor too, and how many people here were crazy about going after him?
In 14-15 Zeller had a fairly consistent role, and he actually played reallywell for us. He gave us 10.2 points, 5.7 rebounds and 1.4 assists in only 21 MPG while shooting 55% from the field and 82% from the line. He had a net rating of +14 that seasons (119 offensive, 105 defensive) - in fact, aside from his rookie year, he's never finished a season with a negative net rating.
If Zeller were to get consistent playing time in the 15-20 MPG range over the course of a season I've got no doubt he'd improve as he develops better chemistry with the other guys on the court. It's been hard for him to do that the past year because he was barely getting minutes, and when he did they were sporadic and unpredictable.
I'm not by any means saying he's a great starting caliber big man - hell no. But as a backup center he's pretty capable if you have the right guys around him, and given how good a locker room guy he has been I think he deserves the right to try and earn a role.
Sully on the other hand had a major role for this team for four years, and (other then his rookie year) didn't manage to get through a single season without constant hiccups and question marks. He's had his chances (and then some) and didn't make the most of them - time to move on.
