Two things to note here:
1) Tennessee polls were waaaaay out in 2016. They had Trump winning it by 10-15 points - and then, he wound up winning it by 26 points.
2) If Trump really is leading by only 9 points... then, to be honest, I find that a little bit depressing. That would mean Biden is overperfoming HRC by 17 points in TN... but there's no polling to suggest that he's doing this nationwide (heck, even that CNN Biden +14 poll is still only a 12-point improvement on 2016). So, this would suggest that Biden is doing disproportionately well in TN... which in turn suggests that he's doing less well in other states (which might be more competitive).
Biden doesn't need to run up the numbers in safe blue states that he'll win anyway, or in safe red states that he won't win anyway. If his popular vote edge is coming primarily from overperforming HRC in these kinds of states (without flipping them), then that's bad news for him.
There's no scenario in which Biden is making Tennessee single digits or close, yet also is losing Wisconsin and Arizona and etc. I wouldn't worry about it.
