Tiki Barber bounced into the end zone with 115 seconds remaining, and for all of the Giants' problems tonight — a running game that went nowhere, turnovers and other mistakes that a young team makes — they had a chance to beat San Francisco.

The game was in the hands of their defense, which had repeatedly turned away one of the best offenses in the National Football League. If the Giants could just hold the 49ers one last time, force the game into overtime, put the ball back into the hands of Kerry Collins. One more stop. One more time.

But a defensive backfield that had played almost flawlessly made a critical mistake, and San Francisco's Jose Cortez hit a 36-yard field goal with six seconds left, beating the Giants, 16-13, in the first game of the N.F.L. season.

It was, in many respects, a perfect manifestation of where the Giants are in their current evolution. Collins threw for 342 yards, wide receiver Amani Toomer had 9 catches for 134 yards, and the Giants' defense held Jeff Garcia to 166 yards passing, reflections of potential.

But there were distinct reflections of their inexperience. Punter Matt Allen, playing the first game of his career, had two terrible punts in the second half, as field position became more critical. The revamped offensive line struggled to cope with the blitzing San Francisco linebackers in the second half, and the Giants mustered just 43 rushing yards on 22 carries. Collins, often under pressure, threw three interceptions.

"They can see what I've been telling them," Giants Coach Jim Fassel said. "We can be successful, but we've got to play smart."

Michael Strahan said: "This is one of those games that comes back to haunt you. You play hard, you play well, and you squander a lot of opportunities on both sides of the ball."

The day began with a Bon Jovi concert in Times Square and an emotional pregame ceremony, and there were questions about whether the N.F.L.'s first Thursday night opener would live up to the hype. But the Giants' defense immediately controlled the tempo of the game.

The 49ers scored 409 points last season, third most in the N.F.L. behind St. Louis and Indianapolis, and Garcia accumulated 32 touchdown and 12 interceptions, becoming a star. As the Giants prepared for this game, they may have drawn on the strategy they used to nearly upset St. Louis last season.

In that game, they rushed the quarterbacks mostly with their down linemen and dropped others on the field back into pass coverage — and this is what they did against the 49ers.

They hounded Terrell Owens, always shadowing him with two defenders; he had only one catch, for a yard, in the first half. Safeties Shaun Williams and Omar Stoutmire ranged quickly and with authority, timing hard hits to break up passes several times.

Garcia stood and waited in the pocket, shuffling his feet, his head turning side to side, without finding anyone open.

"We knew what their game plan was," Owens said. "Take me out of the game."

The Giants stopped drives inside their 10-yard line twice in the first quarter, and incredibly, Garcia had only 66 yards passing in the first half. Matt Bryant had two field goals for the Giants before halftime, and Cortez was 1 of 3 in field goals — one of his attempts was blocked — and the Giants led, 6-3.

Already the Giants realized, however, that they could have had more. Collins threw for 177 yards in the first half, Toomer and Ike Hilliard were running free in the wide-open spaces created by the presence of Jeremy Shockey (who would have 3 catches for 44 yards). With no touchdowns.

But the 49ers began dominating the play at the line of scrimmage in the third quarter, stacking eight and sometimes nine defenders close to the line several times, blitzing constantly. Increasingly, field position became a factor. Midway through the third quarter, Allen botched a punt, hitting it only 24 yards, and later, with the Giants deep in their own territory, he had a rolling 36-yard punt, drawing boos.

San Francisco took over the ball at its 48-yard line, and after Kevan Barlow had a catch and run of 29 yards, the 49ers had the ball at the Giants' 5. The Giants stopped Garrison Hearst for no gain, then an incomplete pass followed. A false start backed up San Francisco to the 9, and it appeared the 49ers might again be stopped close to the goal line.

But Garcia flipped a short pass to Hearst, who caught the ball at the 5 and cut inside, stepping inside the outstretched arms of Micheal Barrow; with a lunge, Hearst stretched the ball across the goal line for a touchdown. San Francisco 10, Giants 6.

"We didn't stop that one drive that gave them seven," Keith Hamilton said later, forlornly.

The Giants trailed, 13-6, when they regained possession at their 23-yard line with 8 minutes 8 seconds to play, and Collins immediately went down on a sack. Barber managed a 2-yard run and the Giants had third-and-16 at their 17, the situation dire, no running game.

"I'm disappointed in how we ran the football," Fassel said. "We've got to run the ball better than that."

But Collins hit Toomer for 23 yards, and after three more completions, the Giants had the ball at San Francisco's 35. Collins lofted a pass over linebacker Derek Smith and Shockey leapt and snared the ball, a 20-yard reception. Barber ran for a first down, advancing to the 5-yard line.

Another run by Barber and the Giants had the ball at the 1 at the two-minute warning. Collins gave it to him again, and Barber — who was questionable before the game because of a strained hamstring — seemed to be out of room. But he cut outside and raced to the corner, scoring. Bryant's extra point tied the game. Collins remarked later how much this drive heartened him, as he looked back on a loss; they had responded down the stretch.

San Francisco started the ensuing drive at the 30-yard line, and on the first play, Owens sprinted into the left flat, where Garcia found him, a 33-yard catch and run to the Giants' 30. Fassel would say later that the Giants had failed to have the shallow zone coverage they expected; Jason Sehorn, the defensive back out in the flat, said the mistake was not his and he did not know who should have been covering Owens.

There was another pass, three more runs, the ball advancing to the Giants' 18-yard line. With 10 seconds remaining, the Giants called their second timeout of the half; after the game, Fassel mused about whether he would have been better off using all his timeouts to give the Giants another chance with the ball.

But it was too late. Cortez jogged onto the field and kicked the ball through. The Giants play St. Louis in 10 days, needing to accelerate their learning curve.
Sep. 6,02