SAN FRANCISCO — Antrel Rolle and the New York Giants studied Alex Smith so much they practically knew what was coming.
On one play in the third quarter, even running back Ahmad Bradshaw screamed from the sideline: ‘‘Trail. He’s watching you.’’ Rolle responded, pretended he was playing the deep ball and sliced in front of Kyle Williams on a short hook.
‘‘He threw the ball right to me,’’ Rolle said.
After a slow start this season, New York’s defense saved its best for the 49ers yet again.
Rolle intercepted two passes by Smith, Prince Amukamara picked off another, and the Giants shut down San Francisco in a 26-3 victory Sunday in a rematch of last season’s NFC Championship game.
‘‘I think this is our most complete game all year long,’’ Rolle said.
After outscoring the Bills and Jets by a combined 79-3 the last two weeks, the 49ers (4-2) met their match again. No overtime needed this time, and not much of Eli Manning, either.
Manning threw for 193 yards and one touchdown, Bradshaw ran for 116 yards and a score, and New York (4-2) rode that dominant defense and four field goals by Lawrence Tynes to hand outspoken 49ers coach Jim Harbaugh the most lopsided loss of his tenure.
The 49ers had not allowed a 100-yard rusher in their previous 22 home games.
The Giants grinded out a 20-17 overtime win at rain-soaked Candlestick Park on Jan. 22, capitalizing on two fumbled punts en route to another Super Bowl title over the Patriots. All week, some San Francisco players talked about ‘‘unfinished business,’’ and Harbaugh added to the hype when he fired off a strongly worded statement criticizing Giants offensive coordinator Kevin Gilbride, who had said All-Pro defensive end Justin Smith often ‘‘gets away with murder’’ holding linemen.
For all the hoopla, the rematch was never close.
Amukamara’s interception in the second quarter started a surge of New York offense. Smith, who wore tape around his sprained middle finger that he said wasn’t an issue, lofted the pass too high and allowed Amukamara to leap underneath the ball before tight end Delanie Walker even had a chance at the Giants 33.
At one point in the first half, Manning completed eight consecutive passes for 142 yards and had the usually stout San Francisco defense out of sorts. Domenik Hixon tip-toed the sideline to catch passes of 39 and 16 yards on consecutive third downs, and Victor Cruz followed with a 6-yard touchdown reception for a 7-3 lead.
‘‘The statement made,’’ Cruz said, ‘‘is that we’re here to stay.’’
Tynes kicked a 34-yard field goal for a 10-3 lead and Tarell Brown blocked a 40-yard attempt by Tynes, which led to David Akers’s miss wide left from 52 yards as the first half expired.
Akers, who tied the NFL record with a 63-yard field goal in a Week 1 win at Green Bay, also hooked a 43-yarder wide right on San Francisco’s first drive. He made a 42-yarder from the same right hash mark. The All-Pro kicker is 11 of 16 this season.
‘‘It wasn’t a great day for any of us,’’ Harbaugh said.
Once the break was over, the Giants sent San Francisco spiraling down and out in a New York minute.
David Wilson returned the second-half kickoff 66 yards to set up Bradshaw’s 1-yard TD run. That quieted the Candlestick crowd — except for the Giants fans that sprinkled the stands blue on a sun-splashed day along the bay.
On San Francisco’s next two possessions, Rolle intercepted Smith’s passes. The first came on an overthrown pass intended for former Giant Mario Manningham that Rolle returned 20 yards to the San Francisco 12. On the second, he stepped in front of a pass to Williams and ran 22 yards to the San Francisco 5.
‘‘I could tell, at times, we had him a little rattled,’’ Rolle said of the 49ers quarterback.
The only downside for New York is it settled for field goals both times.
Then again, not many points were needed.
The Giants sacked Smith six times. Smith finished 19 of 30 for 200 yards, and the 49ers were held to 80 yards rushing.