SAN FRANCISCO — Billed as man vs. machine, Joe Nedney waged a field-goal contest against a robot Monday at Kezar Stadium.

In this corner was the most accurate kicker in 49ers history, a man whose calm under pressure has led to 19 career game-winning kicks. And in this corner was Ziggy, who had nerves of steel—and a body of military-grade titanium.

Ziggy weighs 338 pounds, or roughly the same as the Raiders' JaMarcus Russell. He has a day job demolishing his fellow machines in robot combat competitions, which is why the Canadian native was in the Bay Area. The seventh annual RoboGames kick off Friday at the San Mateo County Expo Center, and Ziggy is the two-time gold medalist in the Super Heavyweight division.

First, though, was his foot-to-foot matchup with Nedney, a brazenly silly publicity stunt that worked well enough to draw the interest of ESPN, the NFL Network and Forbes Magazine, among others.

The rules were simple enough: Each contestant would attempt a field-goal starting at the 20-yard line. If each contestant made the field goal within two kicks, they would repeat the process from 10 yards farther out.

The kicker to make it the longest distance would be the winner, with the loser sold off for spare parts.

Nedney won the coin toss and elected to go first.

"I want to put the pressure on Ziggy," he explained.

Ziggy, though, is tough to rattle, in part because he's constantly surrounded by guys with screwdrivers. In contrast to Nedney, who is 6-foot-5, Ziggy is squat and compact. He checks in at 4› feet long, 3 feet wide and 8 inches high. He looks like a Roomba on steroids. (Performance-enhancing lugs?)

Nedney, going first, wore his familiar No. 6 jersey, red shorts and his cleats. He wasn't kidding around. He took a few rhythmic steps and used his left foot to send a dead-center kick soaring toward the gray San Francisco sky.

"Oh, it's on, baby," Nedney said.

By now, a crowd of a few dozen reporters had gathered on the scene, with as many breathless engineers. (Wired magazine once called the RoboGames "one of the Best Ten North American Geek Fests").

Ziggy was built to handle the pressure. Specifically, he was built to handle a blast of pressure fired from a canister of compressed nitrogen. That's what powers Ziggy's foot—or his "pneumatic flipper," as his engineers call it.

In robot combat, the pneumatic flipper is used as a way of throwing other 340-pound robots just far enough for a fatal crash. "Sometimes they're broken before they hit the ground," says engineer Mike Phillips.

For fun, the engineers dreamed up other uses for the flipper and discovered that the short, powerful burst could blast a football with supreme accuracy. That's when the RoboGames organizers called Nedney and threw down the gauntlet.

Phillips served as Ziggy's holder on Monday. He put an NFL-regulation ball on a tee right near the machine and yelled, "Fire in the hole!" That's the signal for the blast of nitrogen, set at roughly 1,500 PSI.

Ziggy, like former 49ers kicker Ray Wersching, never once looked up at the uprights. He nailed his first attempt, a 20-yarder, although it barely cleared the crossbar.

Both competitors moved back 10 yards. Nedney made his first attempt with room to spare. He taunted his rival again.

"How you doing there, big guy?" Nedney asked.

The answer came soon enough: not well. Ziggy's first attempt from 30 yards was a colossal misfire. The machine made a sickly thud as the ball fluttered as aimlessly as a drunken butterfly.

Something was wrong with Ziggy. "Is there an ambulance on the premises," Nedney wondered. Indeed, engineers scrambled to Ziggy's aid, like a training staff tending to a torn ACL.

Getting Ziggy back to speed took several minutes of trial and error, as well as repeated field-goal attempts that clearly violated the two-attempt limit.

Nedney, a good sport, let it slide. That proved wise because when the competition resumed in earnest, the kicker struggled from 40 yards. His first try was short and his second attempt was wide right. The dreaded words.

The problem was that a cross-wind blew like a gale-force blast one minute and drifted like whisper the next.

But Nedney eventually figured it out. He adjusted his approach, aim and trajectory based on the conditions of the moment and knocked a 40-yarder straight through.

Ziggy tried to duplicate Nedney's success, but the nuances of kicking into a Candlestick-ian wind proved too much to overcome.

"I beat a robot!" Nedney said, raising his hands in triumph.

"Yeah, humans!" another spectator yelled.

Everyone applauded.

Except Ziggy.