The San Francisco 49ers were already without starting quarterback Jimmy Garoppolo. Now, it appears Nick Mullens will miss the remainder of the 2020 season after suffering an elbow injury during Sunday's loss to the Dallas Cowboys.

Matt Maiocco of NBC Sports Bay Area reports Mullens' injury will likely require surgery, and 49ers head coach Kyle Shanahan said Tommy John surgery is a possibility.

Mullens played the majority of Sunday's game, but he was visibly shaken up and holding his arm after making contact with the helmet of a Cowboys defender on the follow-through of a pass attempt late in the fourth quarter.

The 25-year-old was promptly replaced by C.J. Beathard and did not return for the remainder of the contest.

It is pretty unfortunate such a fluky sort of injury could result in surgery. Mullens had done his best to fill in for Garoppolo, but ultimately finished with a 2-6 record as San Francisco's starting quarterback.

Three straight losses have eliminated the 49ers from the playoff chase, just one year after they came within 15 minutes of winning the Super Bowl.

Mullens' late-season injury seems to define a season marred by a number of high-profile physical setbacks. Nick Bosa suffered a season-ending injury in the first game of the year, and cornerback Richard Sherman was placed on IR early on before making his return.

Garoppolo has missed ample time, as have All-Pro tight end George Kittle and running back Raheem Mostert. San Francisco just opened the practice window for Garoppolo, but the quarterback is still on injured reserve due to his ankle injury.

Josh Johnson was expected to be called up to be Beathard's backup, but he was just put on the reserve/COVID-19 list. The 49ers will look elsewhere for an emergency backup quarterback for their Week 16 game against the Arizona Cardinals.