Knee tear said unlikely, but Staley to have MRI

CARSON, Los Angeles County — A week after losing quarterback Jimmy Garoppolo to a season-ending knee injury, the 49ers lost his blindside protector Sunday.

The good news: The 49ers don’t think Pro Bowl left tackle

Joe Staley sustained a torn ACL when he was injured in the second quarter of Sunday’s 29-27 loss to the Chargers.

Staley, who is expected to have an MRI exam Monday, was unable to return to the game and was wearing a brace on his right knee afterward.

Last year, Staley, 34, contemplated retirement during the first half of the season when he dealt with a hip impingement that weakened his quadriceps and placed more stress on his knees. On Sunday, Staley declined to speak with reporters.

Staley’s injury was the most notable on a day in which seven other players were on head coach Kyle Shanahan’s postgame injury report, although rookie wide receiver Dante

Pettis (knee) was the only other player who did not return to the game. Pettis was injured on a punt return in the first quarter.

The other injured players were: wide receiver Marquise

Goodwin (hamstring), offensive tackle Mike McGlinchey (knee), center Weston Richburg (knee), defensive tackle Solomon Thomas (shoulder)

and running back Matt Breida (shoulder).

Quarterback C.J. Beathard also was examined on the field after he was drilled at the end of a 4-yard scramble in the fourth quarter by cornerback

Casey Hayward. Shanahan said Beathard had the wind knocked out of him.

Secondary shuffle: After he was benched the previous Sunday, cornerback Ahkello Witherspoon was involved in a second-half rotation with Greg Mabin.

“It was more about Mabin and how he’s been practicing the last couple of weeks,” Shanahan said. “He had a great week at practice and we thought he deserved it.”

Witherspoon, a 2017 thirdround pick, lost his starting spot after he struggled in a Week 2 win over the Lions. However, he returned to the field when Richard Sherman was sidelined with a calf injury Sept. 23.

In another lineup change, rookie free safety D.J. Reed started in place of Adrian

Colbert, who was questionable with a hip injury. Colbert did play on special teams.

Shanahan said he wanted to go “with the healthier guy” and noted Colbert had been limited in practice after missing Wednesday’s session.

Fast start: There were two firsts on the game’s third play: Safety Antone Exum’s first career interception was also the 49ers’ first pick of the season.

Exum, who was starting his second game in place of Jaquiski Tartt (shoulder), returned Philip Rivers’ wayward pass 32 yards for a touchdown and a 7-0 lead.

“Just by the grace of God I was in the right place at the right time,” Exum said. “I tried to bait him a little bit to make him think I wasn’t there. And he threw it right to me.”

Marathon march: In the first half, the 49ers had a 21-play, 72-yard field-goal drive that took 10 minutes and 44 seconds.

It was the longest drive, based on plays, in the NFL since the Browns had a 21-play drive Dec. 27, 2015. It was the longest drive, based on time, by the 49ers since they had a drive that spanned 12:07 Dec. 30, 2002.