The NFL’s leading rusher in 2023 remains out indefinitely with Christian McCaffery nursing Achilles tendinitis in both legs.

As for the NFL’s leading rusher in 2024, Jordan Mason has a sprained AC joint in his left shoulder. It’s not a serious injury but 49ers coach Kyle Shanahan stopped short of saying he would be ready to play against the Kansas City Chiefs on Oct. 20 at Levi’s Stadium.

McCaffrey, who had 1,459 yards last season, is on injured reserve and will not practice next week although Shanahan said he is “continuing to improve.” Mason’s availability will be sorted out after three days off and a week of practice.

“We take it as good news, but that doesn’t guarantee he’ll be ready to play,” Shanahan said Friday in his weekly day-after call with local writers. “It was positive that it wasn’t worse than that.”

Mason had 73 yards on nine carries in a 36-24 win over the Seahawks Thursday night, giving him 609 yards on 114 carries through six games. Going into Sunday’s games, that leads the NFL in rushing although Derrick Henry of Baltimore is close behind with 572. He was injured with 9:38 left in the half when he landed heavily on his shoulder after a 14-yard gain when hit by safety Julian Love.

Mason left the game but returned in the second half with his left shoulder taped and gained 8 yards on the first carry of the third quarter. He was moving awkwardly after the carry, however, left the game and did not return.

In Mason’s absence, rookie Isaac Guerendo and Patrick Taylor Jr. came on and the 49ers finished with 228 yards rushing, including a 76-yard burst by Guerendo when the 49ers put the game away.

“I thought both did a really good job,” Shanahan said. “We really didn’t miss a beat with it. They kept the rhythm of the offense going. They hit the right holes, ran hard, they were prepared and didn’t hesitate when they got their opportunities.”

While McCaffrey isn’t ready to practice, Shanahan said the 49ers expect to open the 21-day practice window for first-round draft pick Ricky Pearsall Jr., who had been on the non-football injury list since being shot in the chest during a robbery attempt on Aug. 31.

It’s unlikely Pearsall would be activated for the Chiefs game.

“Most likely I think it would be a longer ramp-up period,” Shanahan said. “Healthwise he’s totally good to go. But I really won’t decide until I watch him practice. We’re not going to rush it or anything. If he’s ready he’s ready and if not we’ve got a few weeks.”

The 49ers could also be in the market for another place kicker as Matthew Wright had a dislocated shoulder while attempting to make a tackle on a 37-yard kickoff return by Dee Williams. Shanahan said the shoulder was popped into place, but that an MRI would reveal the extent of the damage.

Wright won the job in a tryout with four other kickers last week when Jake Moody was lost to a high ankle sprain — also while making a tackle on a kickoff return. He was 3-for-3 on field goal attempts against Seattle. If he can’t play, the 49ers may bring back the other kickers who tried out — Riley Patterson, Anders Carlson, Randy Bullock and Matt Coghlin.

Rookie safety Malik Mustapha, who opened Thursday’s game with an interception before suffering an ankle sprain, is day-to-day, Shanahan said.

Shanahan said cornerback Charvarius Ward (knee) and defensive tackle Jordan Elliott (knee), who were inactive against Seattle, were day-to-day. It is hoped that linebacker Demetrius Flannigan-Fowles (calf) will begin practicing this week.

No cigar for Bosa

Nick Bosa is getting close to the quarterback. Next Gen stats had him for 14 pressures of Seattle quarterback Geno Smith, an absurdly high number. He didn’t have a sack, however, and has just three in five games.

The final stat book had him with four tackles.

“Stats sometimes can say a lot and sometimes they can not say anything at all,” Shanahan said. “That’s one of these cases. When I got on the plane and started watching the tape, he was all over. Affecting the quarterback, setting the edge, getting in on tackles. I thought he had a hell of a game. I thought the whole D-line played really well as a group also.”

Bosa was happy with the win, but realizes close but no cigar is not good enough in terms of public perception.

“It’s a finishing business, especially when you’re expected to finish,” Bosa said. “There were a couple of close ones where it was almost ‘ball out, game over,’ ” Bosa said. “I’ve got to keep going. It’s a long year and I’ll look at tape and try and finish those, because that’s what players like me need to do.”

Offensive line in charge

The 49ers’ rushing total of 228 yards was the most in the regular season since gaining 232 against Carolina in 2019 and came despite the absences of McCaffery as well as Mason, who left after nine carries. Quarterback Brock Purdy wasn’t sacked, although he did escape a few times under pressure.

It added up to a big day for the 49ers offensive line.

“I thought they were great,” Shanahan said. “I thought blocking-wise, starting with the O-line but with the tight ends and the wideouts, that’s one of our better games.”

Left tackle Trent Williams can see the progress.

“We’re gelling, and as long as we can keep Brock upright, he’s going to carve the defense up,” Williams said. “As long as we can get the running backs to the line of scrimmage clean, they’re going to fall forward and get yards. We’re not where we want to be, but we’re on a good track.”

Snap judgments

71: Rookie corner Renardo Green, a third-round draft pick, started in place of Charvarius Ward and undercut D.K. Metcalf for a late interception. He had six tackles and two passes defensed. Green had played 33 defensive snaps in the previous five games.

65: Right guard Colton McKivitz and center Jake Brendel were among four who played every offensive snap (right guard Dominic Puni and quarterback Brock Purdy were the others). Both take their share of heat, but they opened the hole that let Guerendo burst for 76 yards to put the game on ice as well as on Kyle Juszczyk’s 6-yard run.

62: Brandon Aiyuk played nine more snaps than Samuel and was targeted four times by Purdy with two receptions for 37 yards. His presence drew coverage that enabled Samuel to be alone for a 76-yard touchdown.

59: Maliek Collins, in part because Jordan Elliott (knee) was inactive, played 59 snaps — the most since he had 60 in Week 3 of the 2018 season for Dallas. He had just one tackle and one quarterback hit but was conspicuous for penetrating the middle of the Seattle offensive line.

58: George Odum, who opened the season as a starter, was forced into action with Talanoa Hufanga on IR and Mustapha injured after 20 snaps. He had six tackles, broke up a pass at the goal line, had an additional pass defensed and also carried a special teams load with 20 additional snaps.

51: Aaron Banks had cramping at left guard, giving way to Spencer Burford, a former starter who had just one snap in his previous four games but had 14 against Seattle.

16: Taylor got his first five carries as a 49er (gaining 16 yards), caught one pass for 12 yards and returned two kickoffs for 45 yards.