AP

When 49ers defensive back Tramaine Brock threw Falcons receiver Harry Douglas to the ground late in the fourth quarter of Monday night’s Candlestick Park finale, it seemed to be a penalty — especially in this safety-obsessed era of pro football.

But throwing the player to the ground, as vicious as it may appear, doesn’t constitute unnecessary roughness if it happens before the ball is dead.

It’s a new rule that was applied to the chagrin of the Texans and defensive back Kareem Jackson in overtime of a September 29 game between Houston and Seattle. Jackson drew a flag for slamming receiver Doug Baldwin to the ground, but the action came after the whistle had blown.

But slamming a runner to the ground becomes a penalty only if the ball is dead. On Monday night, the ball wasn’t dead when Brock threw Douglas to the ground.