49ers Pro Bowl DL Justin Smith reportedly has a torn triceps muscle. (US Presswire)

San Francisco 49ers defensive lineman Justin Smith has a partially torn left triceps, according to a report from the Sacramento Bee.

The injury occurred early in the third quarter of the 49ers’ 41-34 win against New England on Dec. 16, and the 49ers defense has suffered since -- allowing 73 points over the past six quarters.

Smith’s injury had been listed as an elbow issue on the team’s injury reports, and he has not practiced since. With Smith sidelined, Ricky Jean Francois saw the lion’s share of the snaps in the second half against New England and started on Sunday at Seattle.

The results weren’t encouraging for the 49ers’ playoff hopes.

Seattle finished with more rushing yards (176) against San Francisco than any previous game in defensive coordinator Vic Fangio’s two-year tenure.  The 73 points in the six-quarter span is more than the team allowed in its best eight games combined this year (67).

According to the report, the injury will likely require surgery, but the team is hoping he can play through it in the postseason.

Smith was named to the Pro Bowl on Wednesday, his fourth straight selection.

Follow 49ers reporter Kyle Bonagura on Twitter @CBS49ers and @KyleBonagura.