Prime Nishikori was a pretty good returner, so I think he likely bears Fritz and Hurkacz for sure. Rune he could beat as well, but I’m not sure what rune’s level is right now cause he’s been a good returner. Zverev at his best is a better player than nishikori, but Zverev hasn’t been playing at his best. Nishikori could win. Considering how awful tsitsipas has been, nishikori definitely wins here. I think prime nishikori is definitely a better player than rublev, but nishikori was unlucky to face Novak on hard or Rafa on clay for his masters finals. And rublev will mentally implode when nishikori breaks him. Top 4 (especially Novak) are beating him. Keep in mind though, nishikori did beat wawrinka and Djokovic in his amazing 2014 uso run before gassing out. If he plays at that level, he would make it a good match against these 4