FILE - In this Nov. 8, 2009 file photo, a member of the Washington Redskins training staff, top, attends to running back Clinton Portis(notes) after he received a concussion in the first quarter of an NFL football game against the Atlanta Falcons in Atlanta. Thirty of 160 NFL players surveyed by The Associated Press from Nov. 2-15 said they have hidden the symptoms or effects of a concussion so they could continue to play. Portis was not surveyed by the AP.