The New York Giants targeted San Francisco 49er Kyle Williams in Sunday's National Football Conference championship game because of his concussion history, according to two Giants players.

Williams, a wide receiver and punt returner, took a big hit from in the third-quarter and went on to have two fumbles, including the overtime slip that cost his team the game.

"He's had a lot of concussions," Giants wide receiver Devin Thomas told the Newark Star Ledger. "We were just like, 'We gotta put a hit on that guy.'" Thomas went on to praise safety Tyler Sash for landing the dizzying hit. "Sash did a great job hitting [Williams] early, and he looked kind of dazed when he got up. I feel like that made a difference, and he coughed it up."

Jacquian Williams, the Giants linebacker who forced the second fumble, said Williams' previous concussions prompted the hard hit.

"The thing is, we knew he had four concussions, so that was our biggest thing, was to take him outta the game," he told reporters after the game.

It may sound like a sinister strategy, but taking advantage of players' weaknesses is a well-recognized tactic in the NFL. Although teams are required to submit an injury report each week, they make every effort to limit the exploitable details. But targeting a player with a history of concussions - also known as mild traumatic brain injuries - raises the tactic to a dangerous level.

"A brain injury is not like an ankle or knee injury; you can't tape it up," Dr. Allen Sills, a neurologist at Vanderbilt University Medical Center's Sports Concussion Center, told ABC News in August.

Repeated head trauma can lead to chronic traumatic encephalopathy - a progressive brain disease with features of Alzheimer's, Parkinson's and Lou Gehrig's disease. In a class action  filed Jan. 18 in Philadelphia, seven former NFL players claimed the league conspired to conceal the link between football and brain injuries, the Associated Press reported. At least eight similar lawsuits have been filed in New York, New Jersey, Georgia and Florida.