McCarthy pitched in the majors with the Royals every season from 2016-20. He has never gotten swings and misses at the rate one might expect from a reliever, but the sinkerballer has always racked up grounders in bunches and had a couple seasons where he was successful at keeping runs off the board. Over 191 2/3 big league innings, McCarthy owns a 3.80 ERA with a 58.7% ground-ball rate that dwarfs the 43.2% league average for bullpen arms.
Kansas City outrighted McCarthy off the 40-man roster last winter and he elected free agency. The 29-year-old latched on with the Red Sox on a minor league deal and spent most of the year with Triple-A Worcester. He struggled to a 7.13 ERA over 35 1/3 frames, although McCarthy’s peripherals (20.6% strikeout rate, 3.5% walk percentage, 49.6% grounder rate) were far better than that run prevention figure might suggest. The Red Sox released McCarthy last month.
Because Chicago didn’t sign McCarthy until after August 31, he won’t be eligible for the team’s postseason roster. He’ll be on hand as high minors relief depth for the regular season’s final couple weeks instead. If the White Sox don’t add McCarthy to the 40-man roster before the end of the season, he’ll qualify for minor league free agency again this winter.