Stephen Drew was hit in the helmet by a pitch from the Twins' Caleb Thielbar on last Thursday, and before that day was over he began to feel concussion symptoms. This scratched him from Friday's contest, and he has not played since, as Major League Baseball takes concussions seriously these days. In fact, the only reason Drew, who is supposedly feeling better, hasn't played yet is because he's waiting to be cleared by MLB.
The protocols surrounding concussions are fairly new in baseball, as they were instituted league-wide less than two years ago, for the 2011 season. Back when I used to be on the injury beat, I covered this along with athletic trainer Corey Dawkins over at Baseball Prospectus: in short, the National Athletic Trainers Association (NATA) had their protocols used by Major League Baseball in order to determine if someone had suffered a concussion, if they were still suffering from its effects, when it would be safe for them to return, etc. This is one way the seven-day disabled list came about, so as to keep teams or players from feeling the need to rush back from a concussion due to roster issues. In the spring, though, you don't need the seven-day DL, since roster rules are so lax: because of this, Drew just sits out a few games and comes back when MLB says he's ready. MLB's role is the same whether said player is on the concussion DL or not, however:
The medical qualifications have remained constant for some time based on the same NATA position statement, in terms of absence of symptoms and progression of activities. Now they are standardized, and a return-to-play form must be filled out and submitted to the MLB medical director for players with concussions, regardless of whether the player in question was placed on the disabled list. The team must also name an MTBI specialist in the home city, in case any further evaluation is needed.
So, Drew feels better, but that isn't enough. A form must be filled out stating that his symptoms are gone, and MLB's medical director for concussions will go over it and make the proper evaluation, ultimately determining if Drew is indeed ready to return to action.
Drew suffered "just" a minor concussion -- that term is relative, because a minor brain injury is still a brain injury, and some players thought to have just mild concussions have ended up with far more severe and long-term symptoms. Justin Morneau comes to mind as something of the poster child for that. Drew is already feeling better, though, and presumably the Red Sox have submitted the appropriate paperwork. Every time there is a concussion and someone like Drew can get back to playing a few days later, consider it a bullet dodged, and slowly exhale.