The San Francisco 49ers kicked off the ninth week of the NFL season with a bang, as they destroyed the Oakland Raiders in Santa Clara Thursday night, 34-3. However, the 49ers have to take the good with the bad, as they also saw running back Raheem Mostert suffer a gruesome arm injury that took him out of the game for good, according to Ian Rapoport of the NFL Network.

Mostert sustained the injury after getting tripped up on a rushing play in the third quarter. He tried to break his fall with his right arm, which bent in a fashion that was hard to watch.

It was an unfortunate turn of event for Mostert, who was having plenty of success running the ball down the Raiders’ throat before he got injured. Prior to his exit, he had already rushed for 86 yards and a touchdown on just seven carries.

While the 49ers have yet to make an official statement about Mostert’s health status, it’s fair to assume that the 26-year-old tailback is done for the season and definitely out for Week 10’s home game against the New York Giants, considering the gravity of his injury.

For now, the 49ers will rely on the pair of Matt Breida and Alfred Morris for help in the team’s rushing attack.