A heightened awareness of the consequences of brain injuries from playing football have spurred the N.F.L. into taking steps to spot players who might have sustained a concussion. Two certified trainers now sit in a booth above the field, acting as spotters who can communicate over a dedicated radio with a neurological consultant on each sideline.

In a sport as violent as football that is played just once a week, such vigilance might be described as a reasonable cost of doing business.

But what about other sports, where the effects of a brain injury can be as severe but not nearly as frequent?

That issue came to fore on Wednesday night when Yankees left fielder Brett Gardner was not immediately examined after running into an outfield wall in Philadelphia with such force that he was knocked to the ground and shook his head in an apparent effort to clear his senses.