De Los Santos (undisclosed) was placed on waivers Thursday, Jason Mackey of the Pittsburgh Post-Gazette reports.
De Los Santos appeared in 22 games for the Pirates last season and maintained a 4.14 ERA across 24.1innings. He had just an 18:13 K:BB, so his results were fortunate. If he goes unclaimed on waivers, he'll have the chance to opt for free agency.