Yes, Gillaspie is the younger brother of former Sox third baseman Conor Gillaspie.
Casey Gillaspie, a 24-year-old switch-hitter, began the season ranked as the No. 74 prospect in the game, according to Baseball America. He was a Midwest League All-Star in 2015 and a Southern League All-Star in 2016, but he has fallen on hard times this season at Triple-A Durham.
Gillaspie has slumped to a .227/.296/.357 slash line with nine home runs and 44 RBIs in 95 games for Durham. The struggles are a little bit surprising because Gillaspie hit .307 in 47 Triple-A games after being promoted to Durham late in the 2016 season. That's how he got that respectable ranking on the prospects list.
Is the slump this year an anomaly? Possibly. Gillaspie had hit at every level until this year, so we can't count out the possibility that he'll regain his form. He's a former first-round draft pick, so he's obviously got some talent.
And, really, it's not a bad gamble for the Sox, who are parting with a league-average reliever in Jennings. The left-hander is 3-1 with a 3.45 ERA in 48 appearances this season, and he's certainly a respectable bullpen arm. However, Jennings doesn't have much value on the roster to the Sox, who are obviously on their way to finishing well up the track.
Do you really need decent-to-good bullpen arms when there are so few leads to protect? Not really.
For the record, Jake Petricka is the last man standing from the Opening Day bullpen. He's often injured, and thus has little value in a trade. That's probably the one thing that's keeping him in Chicago.