Niners receiver Torrey Smith says he had never been knocked out on a football field before Sunday, when he sustained a concussion in a loss to the Jets.
The Giants placed left fielder Nori Aoki on the seven-day concussion list Thursday, one day after he had to leave the game with symptoms from a head injury sustained last weekend.
Seattle Mariners star Robinson Cano was hit in the head by a stray ball while the Los Angeles Angels were warming up in between innings Saturday and left the game because of dizziness.
Chris Borland is retiring because he concluded the risks of playing football outweighed the benefits, a decision he said he came to after studying brain injuries, concussions and the potential effects of playing football.
Before making his decision, Chris Borland engaged in a season-long dialogue with his parents about playing in the NFL.
Indiana forward Devin Davis was mostly to blame for the car accident that sent him to a hospital with a head injury, police said Monday.
