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Donte Whitner knocked Saints running back Pierre Thomas unconscious in a first-quarter play that altered Saturday's game.

Candlestick Park being what it is – a fan-unfriendly concrete ruin – no one in Upper Reserve 28 had any idea who clubbed Saints running back Pierre Thomas on the first drive of Saturday’s classic 49er victory.

“Who hit him?” fans asked each other, spilling their beers and trading high fives as they looked searchingly to the scoreboard for a replay. It never came, and soon it didn’t matter. The Niners had the ball and the rest -- as they’re already saying, ad nauseam -- is history.

It was only hours later that I saw what 40 million people had witnessed on television: a perfectly legal mugging that altered the course of the game. You can see it here. 

New Orleans quarterback Drew Brees, scrambling to his right, had dumped a pass to Thomas, who took three steps toward the end-zone. Speeding toward him was 49ers safety Donte Whitner. Both men are about the same size and weight – under 6-feet, a little more than 200 pounds.

Thomas was knocked unconscious on impact. The football squirted loose as he crumpled to the ground. As Whitner strutted away, unaware that he had caused a fumble, four or five 49ers jumped on top of Thomas’ motionless body. Linebacker Patrick Willis came up with the ball.

Sportswriters are still searching for the right words to describe the decisive play of San Francisco’s 36-32 stunner: Alex Smith’s bullet TD pass to Vernon Davis with seconds remaining. That’s understandable. But the play that also stays with me was the hit on Thomas, and what it says about these Niners and the NFL.

With the New York Giants coming to Candlestick next Sunday and the Super Bowl on the line, people will undoubtedly invoke the San Francisco Giants’ magical World Series run in 2010. But this isn’t that. The Giants were lovable and eccentric, a team of bearded men and pothead stoppers, impelling their fans to adorn themselves with furry panda hats and funny T-Shirts with the words: “Let Timmy Smoke.”

The 49ers are about raw, unapologetic violence – league-sanctioned violence, celebrated violence, but violence just the same. Alex Smith’s redemption story, and Vernon Davis’ weeping into coach Jim Harbaugh’s shoulder after his touchdown, are compelling human stories. But the 49ers are here largely because of a defense that spent much of this season bludgeoning opponents with the same ferocity that Whitner applied to Thomas.

For the most part, the NFL is a highly lucrative reality series (Fox, CBS and NBC recently renewed their contracts to collectively pay the league more than $3 billion per year). More than 100 million people watch the Super Bowl each year. What we see on our Hi Def TVs is choreographed and glossy, with martial background music and commercials featuring talking babies while players are carted off the field. That’s how most of the country experienced Saturday’s game.

At the Stick, it was a different feeling. You could feel the force of Whitner’s hit throughout the packed stadium. I was near the top of the bowl and I shot out of my seat. It was primal and pulsated through the crowd, energizing us all. Most people were so swept up that it took several moments before we all realized that it was also a fumble, and the 49ers had the ball.

The hit completely changed the game. Whitner was later quoted as saying that the force of it had sent a message to the Saints of the price there was to pay for heading downfield.

Thomas suffered an apparent concussion and didn’t play another down. The NFL determined that the tackle was not illegal because he was not “defenseless” at the time that it occurred. What makes a tackle illegal is codified in a new league rule that bans helmet-to-helmet contact in eight separate categories that define a player as defenseless.

As the 2012 playoffs unfold, the NFL is facing a mounting number of class action lawsuits. Each essentially alleges that the league for years ignored warnings that the game was destroying the brains of hundreds of its players, who have only grown bigger, faster and stronger, amplifying the concussive impact of each collision. The players include such all-time greats at former Steelers center Mike Webster and Bears quarterback Jim McMahon. The crisis is so extreme that what is essentially an NFL brain bank has been established, to study players’ damaged brains after their deaths.

This violence – there’s really no other word for it – is at the heart of the 49ers success this season. We respond to it, because that’s what football is, and that’s how it should be played. I’ll be back out there again next Sunday, cheering for more.