View Photo Gallery: Kyle Williams leaves the San Francisco 49ers’ locker room Monday with his head up.

A day after his two fumbles cost the San Francisco 49ers dearly in their NFC Championship game loss to the New York Giants and made him the target of death threats and vile tweets, Kyle Williams was still calmly and rationally taking all questions.

“It’s one of those things you have to take accountability for,” Williams said. “Everybody is responsible for what they do on the field. It’s something that I was responsible for and I made a mistake, and it’s time to own up to it and move forward.”

Tom Coughlin got a blink-and-you’d-have-missed-it handshake from Jim Harbaugh. (JEFF HAYNES / Reuters)

Williams, who fumbled in the fourth quarter and overtime in the 49ers’ 20-17 loss, said Monday that he was unaware of the threats. His father Kenny Williams, the Chicago White Sox’ general manager, was shocked by the response — and yet he wasn’t.

“I told his mother on the way out exactly what was coming,” Kenny Williams said via ESPN Chicago. “That's the nature of the beast. ... It doesn’t matter what I think, I can’t change it. The only way to change it is to go into another occupation if you can’t deal with it.” Williams added that his son might have been playing with a separated shoulder, but Kyle downplayed that.

“I take full responsibility for the mistake that I did make,” Williams said. “You have to play with what you got. I was dinged up. Everybody was dinged up. That’s just football. Nobody is going to be 100 percent. I was going fine.”

Kyle Williams has a pretty healthy attitude. Maybe now he can teach his coach, Jim Harbaugh, a little something about sportsmanship.

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