It doesn't happen often, but when it does, it's frightening. Dan Jennings of the Miami Marlins was struck in the head with a line drive off the bat of Pittsburgh Pirates shortstop Jordy Mercer in the seventh inning of last night's series finale.
The comeback line drive was estimated to strike Jennings at 101 miles per hour. The Marlins reliever was carted off the field and taken to a nearby Pittsburgh hospital where he was further examined. After a CT scan came back negative, Jennings was diagnosed with a concussion and kept in the hospital overnight for observation.
This was the first such incident since Aroldis Chapman's scary moment in spring training when Royals catcher Salvador Perez hit the Reds closer in the face with a line drive. The teams agreed to no longer continue playing and Chapman was rushed to a hospital in Surprise, Arizona where it was discovered he suffered facial fractures above his left eye and nose. He underwent surgery that inserted a metal plate into his head to help the fractures heal and was luckily only diagnosed with a mild concussion. Chapman was activated from the disabled list on May 10 and has recorded 25 saves in 35 appearances this year with a 2.04 ERA.
In the past few years, pitchers Alex Cobb (Rays), J.A. Happ (Blue Jays), Hiroki Kuroda (Dodgers), Brandon McCarthy (Diamondbacks), Juan Nicasio (Rockies), and others have suffered concussions and head injuries due to comeback line drives. In response to the seemingly growing danger, the MLB approved the development of a protective insert for a baseball hats that can be worn by any player except the catcher (since they already wear a helmet and mask). This insert adds seven ounces to the baseball cap and about a half-inch all around the hat. Here's what it looks like:
The first-ever pitcher to wear the cap in the live game situation was Padres reliever Alex Torres back on June 21. It remains to be seen if the protective cap will ever gain widespread attention and use, but it's a possibility other pitchers and defensive players consider it after last night's incident as well as Chapman's spring training scare.
You can read more about Dan Jennings getting hit in the head by a line drive in this CBSSports article.