NEW ORLEANS — After being in training camp for just two weeks following a 4 1/2-month lockout, the defenses figured to have the upper hand when the New Orleans Saints and San Francisco opened the exhibition season Friday night.

Actually, the defenses had more than the upper hand.

They dominated, especially early in the first quarter when the starters were still in the game, in the Saints’ easy 24-3 victory in the Superdome.

The 49ers’ first 12 plays with quarterback Alex Smith under center netted just 11 yards with no first downs. Things weren’t much better for the Saints, who didn’t produce a first down and gained just 17 yards on nine plays before Drew Brees left the game.

That’s 28 total yards on the game’s first 21 plays and no first downs. At the end of the first quarter, the Saints had outgained the 49ers, 47-23, and Smith and Brees were a combined 2-of-10 for 18 yards in the period.

But the game did have its moments.

Free agent wide receiver Joseph Morgan returned a punt 78 yards for the Saints’ first touchdown and rookie running back Mark Ingram, the second of the team’s two first-round draft picks, darted 14 yards for a score with 1:06 remaining in the first half.

Kicker Garrett Hartley drilled a 47-yard field goal to cap the Saints’ fourth possession for a 3-0 lead before Morgan and Ingram dazzled the crowd of 72,578 — the largest to see a Saints game in the Superdome.

They staked the Saints to a 17-0 lead before 49ers kicker David Akers boomed a 59-yard field goal with one second to play in the first half to cut the deficit to 17-3 at the break.

The Saints tacked on another touchdown in the final quarter when running back Chris Taylor went in from 4 yards out with 8:33 to play.

“Here is what I told the team,” Saints coach Sean Payton said. “I thought there were some good things that we did. I thought we played with good energy, and I thought we did a good job hustling to the ball.

“Aside from being the first preseason game, it was really the first time we got to see these guys in a ‘move-the-ball’ situation.”

The Saints’ first- and second-team defenses had a big night as defensive coordinator Gregg Williams brought lots of pressure early to harass Smith, the first overall pick of the 2005 draft, and rookie Colin Kaepernick.

Smith was sacked twice for 10 yards, while Kaepernick went down four times for 19 yards — all in the first half.

Saints defensive end Will Smith and strong safety Roman Harper got the first two sacks against Smith before the second unit got to Kaepernick almost from the moment he replaced Smith.

Defensive end Jeff Charleston, linebacker Jo-Lonn Dunbar and defensive tackle Mitch King dropped Kaepernick on three consecutive snaps on one series, while linebacker Jonathan Casillas had the final sack.

Payton said Williams dialed up 18 pressures on the first 22 snaps for the 49ers’ offense, which is a high number for a preseason opener.

“We pressured more in the first preseason game than in any of the other five years we’ve been here,” Payton said.

But the sacks weren’t the only damage the Saints’ defense did. Cornerback Terrail Lambert and linebacker Nate Bussey, a seventh-round draft pick, each had interceptions in the second half in Kaepernick’s NFL debut.

“We came after them real early and tried to disrupt them, and we did a great job of that,” Harper said. “Then, the second unit came in and continued to fly around. Any mistakes that we had mentally or anything like that, we made up for by playing fast.”

On the other side of the ball, the Saints’ second- and third-team offenses were more productive than the starters. After Brees went 1 of 4 for 6 yards in his cameo appearance, backup Chase Daniel was 13 of 21 for 129 yards.

“We had three three-and-out drives,” said Brees. “That’s not the way we envisioned it, but we had some manageable third downs. We just weren’t able to convert them.”

Daniel actually got things going after he fumbled the first snap he took from new center Olin Kreutz, who signed with the Saints as an unrestricted free agent a week ago.

Daniel settled down quickly, however, and scrambled for a 19-yard gain on third-and-14 for their initial first down. The Saints were helped on the play by a 15-yard penalty against 49ers linebacker NaVorro Bowman, who crashed into Daniel after he ducked out of bounds.

The net 34-yard gain on the play not only gave the Saints two first downs, it set up Hartley for his 47-yard field goal and a 3-0 lead with 2:31 left in the opening quarter.

After that tough first quarter for the offenses, both teams loosened up a little — especially on the ground.

Running back Joique Bell had a big night for the Saints as he rushed for 52 yards on nine attempts. Taylor added 39 yards on nine carries and Ingram finished with 23 yards on six tries.

The Saints ended the game with 288 total yards to 234 for the 49ers. The Saints’ running game produced 138 yards, while the Niners wound up with 136 yards rushing.

Kaepernick completed 9 of 19 passes for 117 yards and two interceptions in relief of Smith, who was 2 of 7 for 10 yards in a little more than one quarter of play. Kaepernick, however, was the 49ers’ top rusher as the mobile 6-foot-4, 230-pounder netted 47 yards on six attempts.

Morgan, an undrafted free agent from tiny Walsh University in Canton, Ohio, excited the crowd when he fielded a punt from Andy Lee and broke at least three tackles en route to the touchdown.

Using a spin move at the Saints’ 36, Morgan bounced to the outside and sailed down the sideline, cutting back to the middle of the field when Lee failed in the Niners’ final shot at him.

Ingram made a nice spin move on his touchdown as well. The 2009 Heisman Trophy winner took a handoff from Daniel and barged through a big hole in the middle of the 49ers’ defensive line and, after getting into the second tier of the defense, spun away from the last defender at the 49ers’ 7.

“I just have to thank the line for blocking great,” Ingram said. “That’s what really allowed me to get into the end zone. All I had to do was make one guy miss.”