Why are the groundball-heavy Cubs pitchers giving up the long ball?

Cubs: Kyle Hendricks can’t keep it down and has become a liability

Hendricks is perhaps the biggest puzzle. A pitcher who has made his living keeping baseballs on the ground has achieved just a 37 percent grounder rate this year, along with a 4.5 percent homer rate, both career-worsts. Hendricks has the second-highest ERA among qualified starters (5.43), trailing only only German Marquez of the Rockies (6.16).

Hitters have started elevating Hendricks’ once effective sinker.  A pitch that generated 50 percent grounders last season is down to 40 percent this season. Perhaps in response, Hendricks has been replacing some of his sinkers with four-seamers, but that’s always been a flyball pitch for Hendricks, and it is by far his least effective pitch this year, with an xwOBA of .485.

The fastball tinkering is probably more about helping Hendricks set up his curve and changeup. The changeup has been good, but he’s gotten very poor results from the curve this year, although some of that appears be bad luck – the xwOBA for the pitch is a pedestrian .327. Clearly Hendricks and the Cubs are working to address his issues, but for now the veteran right-hander remains a significant home run generator.