Jackie Slater.
One of the points of criticism in 1979 for the local press covering the team was how Slater was not doing well at guard. He was moved to tackle, and in response to the 79 superbowl, Madden at that time said Slater had played the best game at OT he had ever seen from anyone.
Just a little factoid which supports the idea that because someone starts out shaky at guard, that does not mean you know how he will perform at OT.
And another thing about NB and 2019. The entire line started out shaky early in the season and it wasn't just because of newbies on the inside. A team can handle newbies on the inside if both OTs hold up, and they did not. For whatever reason, both AW and Hav started the season out playing below their previous standards.
In fact when the OL improved later in the season, it wasn't just that Edwards and Evans held up, it was also because AW re-stabilized and Hav was replaced by an OT who was playing better.
When an entire OL is shaky, it is impossible for any one individual on that line to look good. I see NB's poor start as being as much an effect of that as anything.
Now THIS year the whole situation with NB is colored by the fact that he is coming back from a knee. Who knows when he will be in optimal form. So that is something they have to account for.