SAN FRANCISCO – Human error.

It caused the 49ers to fall short of a cherished goal of playing in the Super Bowl. It dashed the hopes of a capacity crowd at Candlestick Park on Sunday, as the 49ers lost 20-17 in a breathless, rain-soaked overtime thriller to the New York Giants in the NFC title game.

Kyle Williams, the 49ers' backup punt return specialist, fumbled a kick deep on his team's side of the field, opening the door for the Giants to kick a 31-yard field goal to end it. Williams, only 23 and a second-year player from Arizona State, had already made a critical error earlier in the game.

On a punt headed his way, Williams froze. He neither made a play for the ball nor was able to get out of the way as it hit his knee and was recovered by the Giants, who went on to score a touchdown.

Up until that point in the fourth quarter, it had seemed the momentum was shifting toward the 49ers.

But Williams' mistakes stood as the difference. An entire season, a chance for a lucrative payoff of playing in the Super Bowl, the hopes of 49er fans across the region – all crushed by a very bad day in the life of a very young man.

That is the nature of NFL football and professional sports. The players gifted with elite, natural ability are trained for – and live for – games like Sunday's.

Despite a pelting rain and bracing wind, Candlestick Park was a cauldron of pent-up emotion unleashed in an electric atmosphere.

This old wind tunnel has seen some historic moments, but it was hard to remember when this place was any louder. The 49ers were back after nine years in the wilderness of mediocrity. New coach Jim Harbaugh had returned the 49ers to prominence with a dazzling mixture of intelligence, charisma and optimism.

All season long, Harbaugh's team had won the same way – with a bruising defense and by keeping mistakes to a minimum.

Harbaugh preached this style of play. Through force of will, he got his players to buy into this style of play as if it were a new religion.

But here on Sunday, the Giants matched the 49ers play for play. Both teams were playing vicious, fundamentally sound football.

In games like these, with Super Bowl berths in the offing, each quarter raises the tension level. The crowd grew louder and more rabid. The players on the sidelines seem to enter a trance, their focus so intently acute.

Williams, tall and slender, was the proof that these are still humans playing NFL football. He seemed paralyzed on the punt that grazed his knee in regulation play. He seemed desperate and uncontrolled as the Giants' punt in overtime was stripped from his hands.

When it ended here, Harbaugh shook hands with Giants coach Tom Coughlin and sprinted off the field, barely blinking. It was the end of a difficult day for the Harbaugh family. Jim Harbaugh's brother, John, is head coach of the Baltimore Ravens, who had lost in heartbreaking fashion to the New England Patriots earlier Sunday in the AFC championship game.

Jim Harbaugh was stoic afterward, but he was clearly devastated. "This is going to be a tough one to get over, but we'll get over it," Harbaugh said.

When asked if he had reached out to Williams, Harbaugh said yes. When asked to elaborate, his face grew dark. "I don't feel the need to share that with you."

What was Harbaugh going to say?

The young man made two mistakes and Harbaugh and everyone else pulling for the 49ers to win could only watch in horror.

That was it, the end of months of training and planning.

NFL football is endless hours of meetings and preparation and accounting for every variable in pressure-packed games where split-second decisions must be made before stadiums full of delirious fans.

At the start of overtime, with both teams locked in a 17-17 tie, the rain began falling and 49er fans made an ungodly noise that hurt your hears.

The Giants, to their credit, didn't flinch. They had contained the playmakers and hadn't hurt themselves with errors. That was left to poor Williams. Among this fan base, his name will be recalled ruefully when summing up a year with so many bright spots – a 13-3 season after nine dismal ones. And a thrilling playoff win over New Orleans last week.

It ends with Williams and his desperate and failed attempt to retrieve the ball he had lost. Then it was just a matter of time for a Giants win.

And then, long after everyone had gone, a hard rain began to fall at Candlestick Park – washing away a stadium and a season full of hopes.

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