The San Francisco 49ers’ season may have suffered a mortal blow.

Quarterback Jimmy Garoppolo left Sunday’s game against the Chiefs in the fourth quarter after his left knee appeared to buckle at the end of a downfield scramble.

Coach Kyle Shanahan said afterward that the team is concerned Garropolo tore his ACL.

“Any time you lose your starting quarterback, it is a big deal," said Shanahan.

"So obviously, I feel for him personally. I know how disappointed he is."

The new face of this franchise, Garoppolo was hurt near the sideline at the end of a 13-yard run with 5:27 to go when trying to change direction. He walked gingerly to the medical tent on San Francisco’s bench before being carted to the locker room. He'll undergo an MRI on Monday.

"He told me to lead these guys," backup quarterback C.J. Beathard said of his conversation with Garoppolo following the game.

Practice squad player Nick Mullens is the only other quarterback on the Niners' expanded roster.

Garoppolo signed a five-year, $137.5 million deal in the offseason, making him the league’s highest-paid player at the time. If he’s out for the year, he'd join new backfield mate Jerick McKinnon, who tore his ACL at the end of preseason, on the shelf.

The Chiefs secured a 38-27 win to send the 49ers to 1-2.

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