San Francisco 49ers running back Jordan Mason, the NFL’s leading rusher, left the team’s Thursday Night Football win over the Seattle Seahawks with a shoulder injury.

On Friday, ESPN’s Adam Schefter provided an update on the standout running back.

“The NFL’s leading rusher, 49ers RB Jordan Mason, is believed to have suffered a sprained AC joint in Thursday night’s win at Seattle, which is not considered serious, but he will undergo further testing today,” Schefter reported Friday.

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Mason left the game in the second quarter after falling on his shoulder following a big tackle. He was able to return for one play early in the third quarter before spending the rest of the game on the sideline. Mason had his helmet on and his shoulder taped, but never returned to the game.

Mason has 10 days to prepare for the 49ers’ Week 7 matchup against the undefeated Kansas City Chiefs. If Mason is unable to suit up, the 49ers will rely on rookie running back Isaac Guerendo and fourth-year running back Patrick Taylor Jr.

Mason currently leads the NFL in rushing attempts (114) and rushing yards (609). He replaces Christian McCaffrey, who has not played this season because he is suffering from Achilles tendonitis in both his Achilles tendons. He also had problems with his calf during training camp.

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Additionally, 49ers backup running back Elijah Mitchell is out for the year due to a hamstring injury. That has paved the way for Mason to take the reins of the backfield – and he has been dominant.

Fantasy Football Injury Impact of Jordan Mason Injury

If Mason can’t prepare for the Week 7 game, fourth-round running back Isaac Guerendo would likely take the lead in San Francisco.

Guerendo looked sharp in relief for Mason on Thursday, rushing 10 times for 99 yards. He broke out on a 76-yard run late in the game, but slid inside the five on what would have been his first career touchdown.

“Once I looked at the sideline, everyone was saying, ‘Go down,’ so I had to make a business decision there (to slide),” Guerendo said after the game, via NBC Sports Bay Area.

Is that what head coach Kyle Shanahan wanted?

“Nope,” Shanahan said. ‘We want him to score.’

Guerendo should have plenty of opportunities to score as Mason enters Week 7.

In addition to Guerendo, 49ers wide receiver Deebo Samuel should see some more action in the backfield.

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