It's been known ever since Starlin Castro was shipped to the Yankees for Adam Warren nine days ago that the player to be named later in the deal would be infielder Brendan Ryan.
Thursday, the Cubs officially announced the acquisition of Ryan as that player. Ryan is an excellent defensive player who doesn't hit much; he could wind up as a defensive replacement all over the infield. He really can't hit. I mean at all: .234/.295/.315 lifetime in more than 2,500 at-bats.
Ryan's defense tells his story. He has 15.0 career bWAR. 14.5 of that is from defense. He's the guy who will be the 25th man on the roster, taking on the role that Jonathan Herrera played in 2015. (Not sure if rally buckets go along with that, though.)
To make room on the 40-man roster, reliever Yoervis Medina was designated for assignment. I'm assuming the Cubs are hoping he clears waivers so he can be re-signed to a minor-league deal and invited to spring training.
The Cubs' 40-man roster is currently full, but don't be surprised if other moves come along, waiver and otherwise, soon.