Since your league counts holds, there's no real reason not to give him a shot, especially since you're only dropping Lopez to do it. At the worst, he gives you some decent ratios and the holds you're looking for, while at best he could take over the closer's role and become even more valuable. I haven't completely given up on Riske yet, but he's definitely on thin ice and it's not a bad move at all to grab his most likely successor if he loses the job.
"I'm telling ya, he jumped us. Gloves off, stick down, no warning. He challenged the Chiefs. Called us names. But Dave was there."
"Dave's a killer."
"Yeah, Dave's a killer."
"Dave's a mess."