Brandon Knight undergoes knee surgery; Zack Martin in concussion protocol

The Cowboys once had the best offensive line in football. It wasn’t that long ago.

Center Travis Frederick retired in the offseason. Right tackle La’el Collins didn’t play a snap this season, undergoing hip surgery. Left tackle Tyron Smith played two games but is gone for the season in need of neck surgery.

Joe Looney, who became the starting center when Frederick retired, went on injured reserve Oct. 10 with a sprained knee.

Right guard Zack Martin played only seven snaps Monday, leaving first with a stinger and then with a concussion. He is in concussion protocol, and coach Mike McCarthy said Tuesday, the Cowboys won’t know Martin’s status until later in the week.

Now comes news the Cowboys have lost a third starting offensive tackle.

McCarthy announced Brandon Knight, who has made four starts this season, underwent knee surgery Tuesday after playing all 89 snaps Monday. Knight will miss “a couple of weeks.”

That means the Cowboys will play yet a third left tackle. Left guard Connor McGovern is a candidate, and Cam Erving could be as well, if he is ready to return.

“I think you have to look at all of your capabilities [to figure out a left tackle],” McCarthy said. “I think it’s important for us to try to get some continuity. If Zack can’t go, obviously Connor McGovern will go there, and then we’ve just got to figure out the left tackle position. That’ll start tomorrow.”

Unfortunately for the Cowboys, they face Washington this week. Washington has 16 sacks. Only three teams have more.