If they can only re-sign one of the three O-linemen, Lang makes the most sense. The current right guard is a better option than Sitton, having outplayed him last season. Lang is only a year and a half younger, but has 2,341 fewer snaps of wear and tear on him. Because Sitton has the Pro Bowl and three All-Pro second-team honors, there is a decent chance he will end up making more money. The combination of age, cost, career trajectory, and 2015 production makes Lang the more sensible option of the two guards for Green Bay, if it becomes an either-or situation.
Lang also makes more sense than Bakhtiari. Lang is the better player, and because he is a guard and not tackle, will likely cost less.