Casilla was recently released by the Athletics after making 26 appearances with the club in 2018. During those outings, he logged a 3.16 ERA and 1.21 WHIP while accumulating a subpar 22:20 K:BB across 31.1 innings of relief. The 37-year-old will provide extra depth within the Rockies' system at the Triple-A level.

Casilla was designated for assignment Saturday, and he'll look to latch on elsewhere after being officially released. The 37-year-old right-hander had served as a reliever for the Athletics over the past two seasons.

On the surface, the move is something of a surprise, as Casilla had a solid 3.16 ERA in 31.1 innings so far this season. His underlying numbers were poor, however, with a 16.7 percent strikeout rate and a 15.2 percent walk rate, so his low ERA seems primarily attributable to a .209 BABIP. Joey Wendelken's contract was selected in a corresponding move.

Casilla has yet to issue a walk through that trio of appearances as well, always an encouraging sign for a pitcher with as many control issues as he typically exhibits. The 37-year-old has made significant improvements in both his ERA (2.84) and WHIP (1.07) over last season's respective 4.27 and 1.36 figures, but his fantasy utility remains limited in many formats due to his lack of hold and save opportunities.