The Saints absorbed big hits and four turnovers in the first quarter and trail by only a field goal - 17-14 - at halftime.
The 49ers, who tied for the league high in the regular season with 38 turnovers, had four more in the opening half including one on a knock-out blow on the Saints opening possession. All three 49ers scores took less than a minute and a half.
The Saints, meanwhile, took a more methodical approach. They scored on a nine-play drive that ended with a 14-yard pass from Drew Brees to tight end Jimmy Graham and again on a 25-yard corner-of-the-end zone pass to receiver Marques Colston on a seven-play drive.
A would-be fifth turnover came when safety Donte Whitner seemed to strip running back Darren Sproles of the football. Upon review, however, Sproles was ruled down by contact and the Saints drive continues.
Whitner also forced a fumble on New Orleans' opening drive, which went 12 plays to the San Francisco 7 yard line. Brees threw an outlet pass to running back Pierre Thomas, who lowered his helmet as Whitner approached. The two collided and Thomas appeared to lose consciousness as well as the ball.
The other turnovers came on interceptions of Brees - by safety Dashon Goldson and cornerback Tarell Brown - and on special teams after Madieu Williams stripped returner Courtney Roby.
Alex Smith finished the half 12-21 for 130 yards with two touchdowns and a fumble. His passer rating is 107.2. Brees, meanwhile, was 23-34 for 193 yards. He has a passer rating of 77.2. The Saints have held the ball for 17:51, the 49ers for 12:09. The 49ers will get the ball to open the second half.
-- Matt Barrows