Nationals outfielder Bryce Harper has potentially already suffered an injury in 2014. The 21-year-old slid into second base, breaking up a potential double play, but was legitimately kicked in the head by Mets second baseman Eric Young Jr. in the process.
Harper stayed on the ground after being struck by Young's foot, and it initially looked like he was removed from the game once he did get up. He was just undergoing mandatory testing in the clubhouse, though, with the Nationals giving him the initial concussion questioning: he came back to the field at the start of the bottom of the second inning, so it seems like he's without concussion despite this blow to the head.
It was a potentially scary moment, and hopefully more robust testing doesn't reveal that Harper indeed suffered a concussion during this play. He managed to get away without suffering one when he slammed into a wall last summer as well -- this seems like enough head bashing for one career, Bryce.