SAN FRANCISCO -- Losing the turnover battle served as the 49ers' ready-made excuse Sunday for their most lopsided defeat of coach Jim Harbaugh's tenure: 26-3 to the New York Giants at Candlestick Park.
"Any time a team wins the turnover battle, they have more opportunities to win the game," 49ers cornerback Tarell Brown said.
Alex Smith had three passes intercepted for the first time under Harbaugh, and rather than come to the rescue, the 49ers defense failed to produce any takeaways for only the third time in that 22-game span.
Other factors doomed the 49ers (4-2) in their quest to avenge last season's NFC Championship game defeat to the Giants (4-2). But turnovers overshadowed David Akers' two missed field-goal attempts and the 49ers' suddenly gracious run defense.
"We put ourselves in a position we couldn't come back from, with more turnovers than we're accustomed," Harbaugh said. "We have to bounce back fast."
That's because the 49ers have a short turnaround before Thursday night's visit by the Seattle Seahawks, who have vaulted themselves into a three-way tie for first place with the 49ers and the Arizona Cardinals.
Sunday's defeat marked the 49ers' first home loss in regulation since Nov. 21, 2010, and it promptly erased momentum from their previous two Sundays in which they routed the New York Jets 34-0 and the Buffalo Bills 45-3.
Cornerback Carlos Rogers insisted that this wasn't a humbling defeat because the 49ers' egos already were in check.
"Coach always lets us know that we aren't the kings of the NFL -- it's the Giants," Rogers said. "They won the title last year and are still the team to beat until somebody else wins the Super Bowl."
The 49ers hurtled themselves back into Super Bowl consideration while rolling up 1,000 yards in their previous two wins. Perhaps overlooked in those routs was how the 49ers also combined to force six turnovers while committing only one, a fumble. Last season, the 49ers led the league with a plus-28 turnover margin.
The Giants seized on Smith's uncommon mistakes, converting those three interceptions into 13 points. This was unfamiliar territory for the 49ers, who had only five turnovers (including one interception) their first five games, which opponents parlayed into a lone field goal.
The Giants' turned their first interception -- by Prince Amukamara on a deep pass to Delanie Walker -- into a go-ahead touchdown drive, and Eli Manning's 6-yard strike to Victor Cruz game them a 7-3 lead they would build on all day.
Antrel Rolle intercepted Smith's pass on the 49ers' first two series after halftime, and although the Giants converted those only into Lawrence Tynes field goals, a 23-3 lead looked insurmountable, even with 21 minutes remaining.
"I could tell at times we had him a little rattled," Rolle said of Smith. "But every quarterback is going to be rattled depending on how you disguise coverage."
Smith didn't blame the sprained middle finger on his throwing hand for any of the interceptions. "It was fine," he said of the finger, which he taped around the knuckle.
Coming off his first victorious 300-yard effort, Smith finished 19 of 30 for 200 yards and a season-low 43.1 passer rating. It was his lowest rating since his last three-interception game, on Oct. 10, 2010, against the Philadelphia Eagles.
Colin Kaepernick occasionally relieved Smith for the third straight game, and while that might have crimped any offensive rhythm, Kaepernick did connect with Mario Manningham for a 36-yard pass just before halftime. That half, however, ended in similar fashion to the way it began: with a missed field-goal attempt by Akers.
The Giants preserved their lead by turning to Tynes (four field goals), Bradshaw (27 carries, 116 yards) and a revitalized pass rush (six sacks). Bradshaw became only the second running back in 44 regular-season games to eclipse the 100-yard mark against the 49ers.
"The statement we made was that we are here to stay," Cruz said.
Inside the 49ers locker room, there weren't many shellshocked faces as after last season's finale against the Giants.
"We just have to be mature about the situation, mature about what happened and stay together like we always do," 49ers linebacker Patrick Willis said.
Seattle (4-2) at 49ers (4-2), 5:20 p.m. NFL Network, KGO
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