Querry is at least stylistically interesting vs. Nadal because of that serve and the fact that he can play on grass. Novak-Goffin will be a joke and Roger will steamroll Nishikori on this surface.
Querrey-Nadal is a danger match for Nadal. It will likely be harder than most people think. Following are the stats for Querrey so far:
vs Thiem : 22 aces, 53 winners, 28 UE
Vs Rublev: 26 aces, 55 winners, 17 UE
Vs Millman : 27 aces, 52 winners, 31 UE
Vs Sandgren : 25 aces, 74 winners, 39 UE
Break points saved by Querrey:
Thiem: 6/6
Rublev: 5/5
Millman: 0/1
Sandgren: 4/4
Total: 15 break points saved in 16 opportunities
Querrey has held serve 71 out of 72 times in 4 matches. He has 100+ Aces.
Querrey's been making the QF of Wimbledon regularly. In 2017 Wimbledon Querrey was a few points from making the final.
Given Nadals' (relatively weaker) return of serve and his history against big servers/big hitters on grass - this won't be easy. It's on court 1 and has a similar flavor to the Mueller-Nadal match of 2017.
Also the last meeting b/w Querrey/Nadal in Acupalco - Querrey won in straights on a surface that should have favored Nadal more.
So I'm sure Nadal recognizes the danger and knows that a few slips might be crucial. I think it might be a very close match - harder than the one against Kygrios. Nadal will need to return well and his have no lapses on his own serve.
And yeah: Fed vs Nishi and Novak vs Goffin - can't see anything except routine wins.