Lang, a Pro Bowler last year, missed three games in 2017: one for a back injury, one for a concussion and one for a foot injury. He also sat out a good portion of training camp this year trying to rest his ailing foot. Then he made it through the majority of Monday night's loss to the New York Jets before injuring his back.
Ansah injured his shoulder in the first half Monday against the Jets. An MRI showed no significant damage to the shoulder, a source told ESPN's Adam Schefter earlier this week, and he practiced on a limited basis all week.
On Friday, Ansah told reporters he is "optimistic" he'll play Sunday.
"I would just like to be out there practicing with my brothers," Ansah said. "It's sad. It's sad to be going through this and not being able to be out there helping them win."
Before the injury, Ansah had four tackles and a sack. He has had a history of ailments throughout his career, including needing shoulder surgery in the 2014 offseason, a torn biceps, and knee, ankle and previous shoulder injuries. He began training camp this year on the physically unable to perform list and stayed on it for two weeks before returning to practice.
Despite all the injuries, Ansah usually is willing to play with a degree of pain. He has only missed seven games in his first four seasons, although he hasn't played a full season since 2015, when he made the Pro Bowl.
The situations with Ansah and Lang are the first real examples where a starter has been limited or out all week ahead of a game. First-year coach Matt Patricia, when asked if he needed to have a player practice at least once during the week in order to play Sunday, said it's not as cut-and-dried as that.
"Every situation is different, too, from that standpoint. So, we're obviously trying to get our guys prepared as much as possible," Patricia said. "There are different ways that they are at practice and different ways that they can absorb the information and be ready for practice. And the biggest thing is the level of the experience, I would say, based on the player that affects it from that standpoint. So, if you have a high confidence that guy is mentally prepared, you know physically he's proven that he can go out and play and do those things, then you'll take all that into account before you get to that final decision.
"And sometimes that final decision, it's not a perfect science. It might come right up until game time. You might be working a guy out or checking to see how a guy is feeling because it's really hard to sit here on Friday knowing that we have a lot of hours before we get to a, whatever time it is on Sunday that we play. And then guys' bodies change in different ways, and it's not exact. Everybody is a little different from that accord."