In the last game vs. the Bears Pettine was missing 5 of his front 7 coming into this season (Clark, Daniels, Wilkerson, Perry and Jake Ryan). So, only Matthews and Martinez remain. On top of that King & House, both projected as possible starters at CB coming into training camp (admittedly House more of a nickel or dime, but, most teams consider that a starter) are on IR. Clinton-Dix, a starting S was traded by management, and his backup Whitehead was let go. Two other safeties that might have filled-in, Greene and Campbell are also on IR.
To sum it up, going into the game at CHI, Pettine had four starters left from training camp, Matthews, Martinez, Williams, Alexander. Only Alexander is a plus player, the other three are O.K. (I don't include Brice because it is pretty obvious he isn't starting material at this point in his career [1 sack, 2 pass def., 40 tackles are his 2018 stats...not good] and they were eager to use others in his place every chance they could. No doubt they would have Campbell starting if healthy.)
So, ErIstGute is 100% correct about Pettine doing a "FANTASTIC job". Pettine's D has given the Packers a chance to win in almost every game. If Rodgers had contributed anything vs. the Bears this week, the Packers could have won with a defense almost completely devoid of talent (outside of Alexander). Pettine is AWESOME!