San Francisco @ New Orleans Game Overview

On the positive side, the 49ers rallied late in the fourth quarter to secure a 17-13 road win against division rival Seattle.

But everything didn't turn out as well as the final score.

Star tight end George Kittle suffered a hamstring injury that landed him on injured reserve, kicker Jake Moody missed two field goals that triggered his release, and most significantly, quarterback Brock Purdy sustained toe and left shoulder injuries that will keep him out of Sunday's game in New Orleans.

Purdy, who reportedly will miss 2-5 weeks, was formally ruled out on Friday and Mac Jones will start, with Adrian Martinez as the backup.

"I think Mac knows how to play the position," Shanahan said. "He can play well in the pocket, distribute the ball well, see coverage and can play fast. He's a tough guy who will hang in there and deliver the ball where it needs to go."

Jones started seven games with Jacksonville last season and 42 games in three seasons in New England to begin his NFL career.

He will have to operate without Kittle, but they will have Christian McCaffrey, who rushed 22 times for 69 yards and caught nine passes for 73 yards last week. Tight end Jake Tonges, who caught the winning touchdown from Purdy in the final two minutes, is expected to see more reps.

Eddy Pineiro was signed to replace Moody, who missed a 27-yard field goal, had a 36-yarder blocked and made a 32-yarder.

New Orleans typically uses Alvin Kamara in a similar way to how the 49ers utilize McCaffrey, but Kamara had just 11 rushes for 45 yards (with an 18-yard touchdown) and two catches for 12 yards in a 20-13 loss to visiting Arizona last Sunday.

"Obviously, we want to get him more involved," quarterback Spencer Rattler said of Kamara.

The Saints had a chance to match the 49ers' late comeback but fell short in Kellen Moore's debut as an NFL head coach. Blake Grupe's field goal brought the Saints within a touchdown, and Rattler led them to the Cardinals' 18 in the final minute, but his fourth-down pass sailed out of bounds as time expired.

Moore cited getting one touchdown out of four trips into the red zone and converting just 5-of-14 third downs as areas where the team must do better against San Francisco.

New Orleans' third-down struggles were partly caused by penalties that placed the team in long-yardage situations. The Saints were flagged 13 times for 89 yards, with nine of those penalties being pre-snap infractions.

Rattler said the rash of penalties "woke us all up."

It led Moore to bring local officials to practice this week to call "any detail" that might have led to a penalty being called in a game.

Four Saints starters are hurting. Left guard Trevor Penning (toe), defensive end Chase Young (calf) and safety Julian Blackmon (shoulder) were ruled out; Blackmon was injured in the opener and will have surgery this week, which could end his season. Right tackle Taliese Fuaga (knee) was limited Thursday and Friday after missing Wednesday's practice and is questionable for the game.

49ers wide receiver Jauan Jennings (shoulder) and left tackle Trent Williams (knee) are questionable.

--Field Level Media