SAN FRANCISCO — The 49ers opened their pocketbooks in the offseason to keep their highly rated defense intact and to completely retool their receiving corps, all with one goal in mind — to bridge the small gap that kept them from being the best team in the NFL last year.

Judging by Sunday's 26-3 loss to the New York Giants at Candlestick Park on Sunday, the gap may have actually widened.

Almost nine months after the Giants came into this stadium and outlasted the 49ers in overtime in the NFC championship game, the defending Super Bowl champs recorded a much more emphatic victory. New York dominated every phase of the game, intercepting Alex Smith three times, chewing up yardage at key points of the game and dominating on special teams.

"It hurt. It hurt a lot," tight end Vernon Davis said. "We expect to go out there and get the win, but we couldn't pull it off for some reason. Have to go back and look at the film. But I'm sure we made a lot of mistakes. We cost ourselves the game."

It was the worst loss of the Jim Harbaugh era, and it was especially baffling on the heels of successive blowout wins over the Jets and Bills. Last week, the 49ers set a franchise record for total yardage. This week it was Harbaugh's team that got buffaloed.

"I don't know that I have the lesson learned right at this moment," the somber coach said afterward.

The Giants controlled both sides of the line of scrimmage after the first quarter, running off 26 consecutive points to put the game out of reach.

Down 3-0 at the start of the second quarter, New York quarterback Eli Manning took over. He completed 10 of 13 passes for 159 yards and a touchdown to Victor Cruz during the quarter, frequently picking on cornerbacks Chris Culliver and Tarell Brown. Manning wound up with 15 completions in 28 attempts for 193 yards. He wasn't sacked once.

If Manning slowed his pace in the second half, it hardly mattered, because the usually impenetrable 49ers run defense sprang some leaks. Ahmad Bradshaw finished with 116 yards on 27 carries, a rare 100-yard day against defensive coordinator Vic Fangio's unit, with 56 yards coming in the fourth quarter when San Francisco desperately needed to stop him.

Things didn't go a whole lot better on the other side of the ball. Alex Smith, who had offered up just one interception in his previous 10 games combined, was picked off once by cornerback Prince Amukamara and twice by safety Antrel Rolle. Smith's 43.1 passer rating was his lowest since Dec. 20, 2009, against the Eagles.

"We had a few turnovers," safety Donte Whitner said. "Statistics show when you lose the turnover battle three to zero, it's like an 80-plus-percent chance that you're gonna lose the ball game. We have to get more turnovers on defense and give our offense a short field."

The Giants did not turn over the ball once.

Smith had sprained the middle finger of his throwing hand in last week's rout of the Bills, but insisted it did not affect his passing Sunday. Really, his decision-making seemed worse than his accuracy on the interceptions.

The 49ers quarterbacks also were under steady pressure from New York's ferocious front four. Smith went down four times and backup Colin Keapernick twice, though the Giants rarely blitzed. Defensive end Jason Pierre-Paul had two of the sacks.

The 49ers dominated the line of scrimmage early in the game, but had little to show for it. San Francisco's first two drives ate up 11:24 of clock time and 120 yards of turf, but both stalled inside the New York 30-yard line. David Akers attempted field goals each time, missing the first from 43 yards and nailing the second from 42.

The 49ers outgained the Giants 120 yards to 25 in the first quarter, but held a meager 3-0 lead.

New York finally got rolling in the second quarter, following Smith's first interception. Two passes from Manning to Domenik Hixon, of 39 and 16 yards (both on third down, and both against Culliver), set up a 6-yard touchdown pass to Victor Cruz.

Up 10-3 at halftime, the Giants made a loud statement to start the third quarter, using a 66-yard kickoff return by rookie David Wilson as a springboard to Bradshaw's 1-yard touchdown plunge. The only scoring after that came on 30-, 22- and 32-yard field goals by Lawrence Tynes.

By the end of the game, the 49ers fans had mostly cleared out of the stadium, leaving a sizable contingent of blue-clad boosters to chant "Let's go, Giants!" They weren't offering support to the team at AT&T Park.

Perhaps thankfully, the 49ers don't have much time to lick their wounds. They host Seattle on Thursday night, and the Seahawks will be fired up after a 24-23 victory over New England on Sunday.

"We'll be ready," Whitner said. "We'll get this bad taste out of our mouth."

You can reach Staff Writer Phil Barber at 521-5263 or phil.barber@pressdemocrat.com.