METAIRIE — The next-man-up mantra the New Orleans Saints and every other NFL team preaches took on a whole new meaning during a crucial time in last Sunday’s game with the Oakland Raiders.

The Saints, who have four tackles on the active roster, had only three available Sunday because starter Zach Strief was sidelined with a groin injury.

Then, during a two-minute drive at the end of the first half when the Saints were trying to double a seven-point lead, third-year pro Charles Brown went to the bench with a knee injury.

Suddenly, the next man up — 6-foot-6, 300-pound rookie Bryce Harris — became the last man standing on the right side.

Harris, who had yet to play a snap in the regular season, struggled on his first two plays when the Raiders applied heavy pressure to Drew Brees.

But Harris’ third play, on which he got some help from tight end Jimmy Graham, ended with Brees getting enough protection to launch a 38-yard touchdown pass to Lance Moore.

“I thought Bryce did a good job last week,” said Strief, who was limited in practice Wednesday for the first time since being injured on Nov. 5. “He got tossed into the fire in the middle of a two-minute drill. That’s less than ideal, and I felt his pain because I’ve been in that position before.

“It’s not easy physically and it’s not easy mentally, especially when you’re your first reps in a live game,” he added. “But he’s a really good athlete and a strong player.”

By all accounts, Harris, who was signed off the Atlanta Falcons’ practice squad on Sept. 10, did an admirable job in the second half of the Saints’ 38-17 blowout of the Raiders.

If Strief can’t get back into the lineup by Sunday, Harris will be put to the extreme test when the Saints face the San Francisco 49ers in the Mercedes-Benz Superdome.

The 49ers, who rank second in fewest yards allowed, have one of the NFL’s top pass-rushers in outside linebacker Aldon Smith.

After destroying the Chicago Bears on Monday night with 51/2 sacks and two forced fumbles, Smith, who has a league-leading 15 sacks this season and 29 in his first 26 games as a pro, was named Wednesday the NFC Defensive Player of the Week.

While the numbers are disconcerting, Saints interim coach Joe Vitt said he’s only concerned with his team.

“I can only be concerned with what we have and who we’re going to line up with,” Vitt said. “We had a good practice today. They have outstanding pass rushers, and you all saw it Monday night.

“They’ve got great edge pressure and they’ve got strong people in the middle that can get in Drew’s face. Our ability to create a firm pocket for Drew is going to be critical. But listen, we worked long and hard on it today and we’re going to get their best … they’re awfully good.”

When asked if providing Harris with some help against Smith will be a necessity, Vitt said, “It’ll be in our plan. It’ll be in our plan.”

But Vitt said Harris wasn’t all that bad on his first few snaps.

He said Harris had good protection initially on one of the passes, but the defender backtracked around and hit Brees after he delivered the ball.

“I don’t know if Zach, or Stinch (former Saints tackle Jon Stinchcomb), or anybody is going to make that play,” Vitt said of Harris, who was not in the locker room Wednesday during the time it was open to media.

“So, (Harris) was OK for the first time, and he’ll get better this week.”

Vitt said the Saints, who lost rookie tackle Marcel Jones late in training camp to a knee injury, were attracted to Harris’ athleticism and footwork for a big man when they went searching for a fill-in.

He said it helped that Harris lined up next to three-time All-Pro right guard Jahri Evans because Evans is a good communicator on the field.

“I don’t think he was nervous at all,” Evans said. “I think he was confident, and the one thing I tried to tell him was to take good sets and have physical hands. I told him to be ready for what he was going to see and believe in his ability.

“He did a good job. He just went in there and showed why he deserves to be here. You’re going to get the other guy’s best pass-rush moves in the two-minute drill, but there were no jitters on his part.”

Brees certainly noticed.

“I thought he did great, especially for a guy who hasn’t been here that long,” he said. “He’s just been running the scout team and really hasn’t gotten any reps with the first team, and all of a sudden he’s thrown in the mix.

“He was very calm and comfortable, a lot more so than I felt like typically a young guy getting his first action would have been.”