The NFL's leading player in 2023 is out indefinitely with Christian McCaffery suffering from Achilles tendonitis in both legs.

Jordan Mason, the NFL's leading rusher in 2024, has a sprained ACL in his left shoulder, so it's not a serious injury, but 49ers coach Kyle Shanahan didn't say he would be ready on Oct. 20 to play against the Kansas City Chiefs at Levi's Stadium.

McCaffrey, who had 1,459 yards last season, is on injured reserve and won't practice next week, although Shanahan said he “continues to improve.” Mason's availability will be determined after three days off and a week of training.

“We think it's good news, but that doesn't guarantee he'll be ready to play,” Shanahan said Friday in his weekly call with local writers. “The positive thing was that it wasn’t worse.”

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

Mason left the game but returned in the second half with a taped left shoulder and gained eight yards on the first run of the third quarter. After the carry, he moved awkwardly but left the game and did not return.

In Mason's absence, rookies Isaac Guerendo and Patrick Taylor Jr. stepped up and the 49ers finished the game with 228 yards rushing, including a 76-yard burst from Guerendo as the 49ers put the game away.

“I thought they both did a really good job,” Shanahan said. “We really didn’t miss anything. They hit the right holes, ran hard, were prepared and didn’t hesitate when the opportunity came their way.”

While McCaffrey isn't ready to practice yet, Shanahan said the 49ers expect to open the 21-day practice window for first-round draft pick Ricky Pearsall Jr., who has been on non-football play since being shot in the chest. The list of injuries included an attempted robbery on August 31st.

Pearsall is unlikely to be activated for the Chiefs game.

“Most likely I think there would be a longer ramp-up period,” Shanahan said. “His health is completely fine. But I really won't decide until I watch him train. We're not going to rush it or anything. If he’s ready, he’s ready, and if he’s not, we’ve got a few weeks.”

The 49ers could also be in the market for another place-kicker since Matthew Wright suffered a shoulder injury attempting to attack a 37-yard kickoff return from Dee Williams. Shanahan said the shoulder was pinched, but an MRI would show the extent of the damage.

Wright won the job last week in a tryout with three other kickers when Jake Moody was sidelined with a high ankle sprain – including a tackle on a kickoff return. He went 3-for-3 on his field goal attempts against Seattle.

Rookie safety Malik Mustapha, who opened Thursday's game with an interception before suffering a sprained ankle, is in day-to-day routine, Shanahan said Friday.

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

QUICK JUDGMENTS

65: Right guard Colton McKivitz and inside linebacker Jake Brendel were among four players who played every offensive snap (Puni and Purdy were the others). Both got their share of the heat, but they opened the hole through which Guerendo burst 76 yards to put the game on ice and on Kyle Juszczyk's 6-yard run.

62: Brandon Aiyuk played nine more snaps than Samuel and was targeted by Purdy four times, intercepting two balls for 37 yards. His presence provided coverage that allowed Samuel to score a 76-yard touchdown alone.

59: Maliek Collins, partly because Jordan Elliott (knee) was inactive, played 59 snaps, the most since he had 60 for Dallas in Week 3 of the 2018 season. He only had one tackle and one quarterback hit, but excelled at getting to the middle of Seattle's offensive line.

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