I like Nunes more than most, and have defended him on here, but I still feel like going into the season with him as our primary RB option is asking for trouble.
He can clearly play as a RB, he's improved, and I'm very happy for him. He brings some strengths to the position and I think he can be a solid part of the squad.
But I would be absolutely terrified of him going up against the best left sided attackers in the world. Vini, Kvaratskhelia, Nico Williams - even the Anthony Gordon's & Luis Diaz's would terrify me. When Walker was in his prime (& even a bit past it), and we were at our best, we could rely on him to match up with that level of player. It was a big part of what made us so good. I just don't think Nunes consistently can do that, and it'll become an exploitable weakness that teams will target.
I'd be genuinely thrilled to be proven wrong. But I think not addressing the position would prove to be a costly mistake.