KYLE WILLIAMS . . . the backup punt returner who basically lost the game for the San Francisco 49ers has been getting death threats on twitter....really people...its just a game! 

NBC reports that several people directed "hateful messages and threats" at Williams on Twitter . . . including some that specifically talked about wanting him to die. 

NBC said that "many of those" were taken down.

Williams hasn't commented on the threats, but the NFL is keeping an eye on it.

The NFL says they take "any threat seriously" . . . and adds that they've been in touch with the 49ers and law enforcement.