The remodeling has been frequent on the Green Bay Packers' offensive line in recent years.
There have been waves of injury, departures in free agency and even a retirement, but quarterback Aaron Rodgers and the rest of the offense have adapted to the new surroundings each time.
There has been one exception to the rule. For more than three seasons, the constant has been Josh Sitton and T.J. Lang. Together, the guards have missed only three games as starters with Sitton having played 86 of 88 games since 2009 and Lang 55 of 56 since 2011.
That could change Sunday against the Chicago Bears with Sitton battling a torn ligament in his left big toe and Lang out with a sprained ankle he suffered against New Orleans. Both veterans sat out Wednesday's practice.
"It's a blow. Those guys are very talented," Rodgers said. "They're having great seasons, Pro Bowl seasons. But it is next man up. No one's going to feel sorry for you or wait around for you. You have to step up and be a professional and be ready to play. That's what being a backup is all about."
On the opposite side of the locker room, JC Tretter and fellow reserves Lane Taylor and Garth Gerhart understand what could be asked of them against the Bears.
Tretter was activated off temporary injured reserve Monday. He was slated to be the team's starting center before injuring a knee in the third preseason game. Now, the Packers are positioning Tretter to step into the utility role Don Barclay vacated after tearing his ACL in training camp.
The only problem is Tretter has yet to play in an NFL game. He broke his ankle during the first day of organized team activities last year as a rookie.
Still, the Packers have confidence in the Cornell graduate's athleticism and intelligence. At 6-foot-4 and 307 pounds, he's not built like an NFL left tackle, but the team lists him as the backup to David Bakhtiari on the depth chart. After working at center throughout the offseason, he also could be asked to step in at guard as soon as Sunday.
Tretter worked all across the line during the two weeks he was allowed to practice before his midseason activation. Aware of what they were facing with Sitton and Lang, the organization still felt comfortable enough to promote Tretter and part ways with tackle Derek Sherrod, their 2011 first-round draft pick.
"That two-week window with the bye was definitely important," Tretter said. "I think we utilized it well getting comfortable everywhere. A lot of that was just moving to a different position, so you could get a different body movement that you can't get running scout team where you can't control what the other team runs."
Taylor had played mostly special teams before being summoned when Lang injured his ankle on an extra-point attempt. The 6-3, 324-pound guard was serviceable in pass protection, but struggled in run blocking.
The play many pointed to was Saints defensive tackle Tyrunn Walker blowing past Taylor when the Saints stuffed running back Eddie Lacy for no gain on fourth down with 3:32 left in the third quarter.
On Monday, Packers coach Mike McCarthy made it clear Taylor "needs to perform better" if his number is called against the Bears, but whatever first-team reps he sees this week should help his progression after jumping in cold against the Saints.
"I'm very confident in Lane just from watching the way we played," Sitton said. "I mean, the way it unfolded, he had one play that kind of stood out to everybody but he actually played well. I haven't seen JC play a whole lot of guard, but I didn't see him play a whole lot of center and he came in and was able to play well, so we're confident in all the guys we have rotating."
Rookie center Corey Linsley knows how difficult it can be to step into a starting role. After all, that's what was asked of him after Tretter went down.
Eight games into his NFL career, Linsley would be the Packers' longest-tenured interior lineman if Sitton and Lang are unable to play. He didn't take his first in-game snap with Rodgers until the opener against Seattle, but has played well to this point.
Lang and Sitton helped him with his calls and checks early this season, but Linsley has become less reliant on them as the season progressed. He laughs when admitting it would be "stupid" not to tap into the veterans' knowledge base, but he believes he'll be OK if he has to go it alone, too.
"Every week, I'm feeling more comfortable, more comfortable," Linsley said. "Obviously, I think Josh and T.J. are going to be back, but who knows exactly? We have to prepare like they won't be here. If they aren't, it'll be a huge test for me and also JC and Lane. It'll be a crazy week."
If either Lang or Sitton is able to play, the Packers would have to determine if they want to green light Tretter for his first NFL action or stick with Taylor.
The young interior linemen hope there wouldn't be too drastic of a drop-off if Sitton and Lang don't play, but they're also realistic. Pro Football Focus rates Sitton (third) and Lang (tied for eighth) among the top pass-blocking guards in the NFL this season.
There's been a lot of turnover on the offensive line. Rodgers has had four starting centers in as many years. Bryan Bulaga and Barclay suffered torn ACLs. Marshall Newhouse and Evan Dietrich-Smith left in free agency.
Still, the offensive linemen pride themselves on their continuity. If Lang and Sitton can't go, it's just another test.
"They're two of the best in the league," Linsley said. "We've got to prepare so that the drop-off initially — because anybody in the league would be a drop-off from Josh and T.J. We'll prepare so that we're ready for Sunday. That's what practice is for and that's what we have to do."
— firstname.lastname@example.org and follow him on Twitter @WesHod.