For my money, among players who aren't NextGen-age (so no Korda) and are at or around their career high ranking (so no Nishikori or Kyrgios), Ivashka is the most underranked player in men's tennis. I expect him to beat Ymer, but certainly Ymer has a chance. I didn't expect him to beat Tiafoe or Alcaraz, either, yet here we are. His first serve and forehand are looking a bit beefier (a technical term) than I remember them being.
I don't think Ivashka's run's that much better than Ymer's:
Ivashka's win against PCB looks impressive on paper (didn't see the match or highlights), and there are some big hitters on his list. But he hasn't faced a patient ball retriever and counterpuncher like Ymer so far. Imo, Ymer's closer to Simon than f.inst. PCB. And Ymer has show impressive mental strength by staying patient against a huge hitter like Alcaraz (he's even beaten him earlier this year).
"With toolbox I have and the way he plays, [wearing him down] is more or less the only option, because he's so aggressive," Ymer said. "I think I executed the plan pretty well."
I don't think it will be easy for Ivashka to hit through Ymer, and he won't be discouraged if he's behind on the scoreboard, as this is something he is used to, and has been able to turn around several times. Not so sure about Ivashka in that position.