I don't quite get the Serge hate on this board. Is it because he looked terrible against us? I'm guessing so. It was easily his worst game of the season, and probably years. He went for 12/7 their next game in a win at Toronto. Bad games happen.
Anyway, his DRB% isn't spectacular, but it's still as good as anyone on the Celtics, and is above his career average. He's never been an elite defensive rebounder, but he hasn't experienced a significant decline. His blocks are down from his old astronomical levels, but he's still 13th in blocks per game and 14th in block percentage. You're not likely to get better than that on the trade market.
He's playing a bit further from the rim on offense than he used to, shooting many more 3s. But a) he's hitting a career high 38.4%, b) the Celtics would certainly ask him to take 3s, and c) welcome to the NBA in 2017. He's still a good finisher at the rim (72% FG% at rim.) He's a plus FT shooter (82%).
He's healthy (missed only 1 game this year and played 78 games last year.)
Against Cleveland, he'd give us the offensive mismatch that we get with Horford and Jerebko on the court together, without the defensive mismatch against Love and Thompson.
He's not Boogie, I get that. He's not Milsap. I get that too. But he'd help our weakness (defensive boards, interior defense) without hurting our strength (spacing on offense). He's a good fit. I wouldn't break the bank for him, but Zeller, a non-Brooklyn 1st in 2018-2019 (or Yab), and Mickey/Young/Jackson for salary purposes (Zeller makes $100k too little to trade straight up. It's tragic) is a reasonable price to make our good team better. It doesn't cost much in terms of assets, and it doesn't kill long-term flexibility.