Ziegler didn't start out as the Diamondbacks' closer last season, but he took over and was very effective after Addison Reed was relieved of his duties. Ziegler notched 30 saves and a 1.85 ERA, so he was definitely fantasy relevant. However, you always feel like you're playing with fire when Ziegler is on the mound since his stuff doesn't blow anyone away. With a below average fastball, and weak 4.8 K/9 ratio, Ziegler has to pitch to contact a lot. While he can still be effective doing so, it also opens up the possibility for balls finding holes in the defense. The lack of velocity also means that when a hitter connects, he will likely do some damage.
That being said, it seems that it is Ziegler's job to lose right now. The pitching staff is upgraded so he will likely have some more save opportunities. He shouldn't be one of the top closers off the board, but he can have sneaky value for anyone who drafts him late. Just be wary that because of his age and style of pitching, it's very possible he doesn't finish the season as the closer.