The 49ers ended up beating the Cowboys 30-24. Guerendo finished with a game-leading 85 rushing yards, averaging an impressive 6.1 yards per carry.
Mason has been managing an AC joint sprain from Week 6 against the Seattle Seahawks. After Sunday's game, head coach Kyle Shanahan noted that Mason's latest injury was to the same shoulder.
"JP (Mason) got banged up," Shanahan said. "JP tried to come back, and maybe could have, but Isaac was rolling and did a good job."
Additionally, linebacker Dee Winters suffered a concussion, wide receiver Deebo Samuel exited with a rib injury, and cornerback Renardo Green sustained an ankle injury. Shanahan stated he didn't yet have details on the severity of Samuel and Green's injuries.
Samuel was questionable to play against the Cowboys after a recent hospitalization for pneumonia but was active for the game.
The 49ers have been hit hard by injuries this season, with 10 players currently on injured reserve. The latest setback came with wide receiver Brandon Aiyuk, who is out for the season due to a torn ACL and MCL.
San Francisco could see some players return after the bye week. Running back Christian McCaffrey, sidelined this season with Achilles tendinitis, is expected to resume practice, along with wide receiver Jauan Jennings, who has missed the last two games with a hip injury.
The 49ers' next game is on November 10, when they face the Tampa Bay Buccaneers at Raymond James Stadium.
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