We always have this issue it seems we have a chance for an 'up' year, except for 2014:
1998-2000: Were missing a QB. When we got one, the lines fell apart in 2001-2003. Yeah, I know we went 9-2 in 1999 but the schedule that year was easy and we got lucky - A LOT.
2010: Missed on Cam. While Relf did fine, he's not Cam and thus would have needed the WRs to be elite, and they just weren't at that time. Had everything else.
2015: Needed another lineman or two, even though Dak overcome a lot of it.
2017-2018: Needed a big play WR (AJ Brown would have been money). Of course we lost Rankin after 2017 too, and Eiland ended up being a turnstile.
So much of the season riding on Dolla Bill. I'm not worried about the loss of Polk at all. Good news is that with Cole Smith winning RG, the whole OL are 4th year players with a ton of starts. That's got to mean something. Backups aren't chopped liver either.