McDonald is actually playing really well on grass and has started to turn his season around with this surface. Rune hasn't had a ton of court time recently, but his serve is still as powerful as ever. I think the more likely scenario is that this one goes long and we see the over hit.

The Rune vs. McDonald match is likely to go under 9.5 first set games due to both players' strong serving on grass. Rune’s 79% first-serve win rate and McDonald’s 74% in recent matches suggest few breaks. Their aggressive playstyles and quick points on grass courts typically lead to shorter sets, with tiebreaks or 6-3/6-4 scorelines common, keeping the first set game total low.

H. Rune is just inside the top 10 while M. McDonald is just inside the top 100 in the ATP-Tour these days. Keep in mind that the h2h is tied at one a piece right now. I believe that the underdog got some chances on grass. Bet on first set M. McDonald to win.