It’s a dangerous game. Bryan Mitchell was forced to leave a home game Monday after a line drive from Minnesota Twins shortstop Eduardo Nuñez connected with his face. The impact sent the 24-year-old prospect to the ground, and his trainer helped him from the field. Diagnosed with a broken nose, Mitchell is being monitored for signs of a concussion. He’s one of four pitchers to be hit in the head this year, raising the issue of whether they need protection — other than a padded cap only one of them wears.