Both semi-final matches will be very interesting to watch and hopefully they both live up to the hype!
For the Medvedev-Nadal match, for me personally, it comes down to "mental" approach at least on Medvedev's side. He is playing very well right now, he has won 8 matches in a row and 8 sets in a row. He is playing both aggressively and tremendous defense! He has the tools to beat Nadal especially on an indoor hardcourt, but the main question for him is can he finish the job? Last year, he was up 5-1 and had match point on Nadal's serve and he mentally "choked" away the match. You know he is definitely thinking about that loss. This is a great opportunity for Medvedev to exercise those mental demons against Nadal.
As for Nadal, just to continue to serve well and keep being aggressive especially on the backhand side. Just like the match-up against Tsitsipas, he does not mind this match-up against Medvedev because he can use slice and net approach to throw Medvedev off his rhythm. The one important shot that Nadal has to do well tomorrow night is his return of serve. Unlike Tsitsipas, Medvedev can get "hot" on his own serve meaning he can finish his service games in a minute. And if you know Nadal, if he can not feel his return of serve shot, he gets nervous and tentative. When he gets nervous and tentative, then he shanks his forehand and hit his forehand way short. Nadal has to put the ball in play or else Medvedev will beat him maybe in two sets.
All in all, I am excited for this particular match! I hope it is a fun match and may the best player wins! Vamos!