Its going to be a lot tougher for Tsitsipas than it is for Nadal, that is for certain.
Let's face it, Tsitsipas has never solved Nadal.....and even his win this year at the AO was the most unconvincing win of all-time, down 2 sets to 0 and did not win a point on Nadal's serve in the 3rd Set until the 12th game. And the 4th and 5th Sets could have gone either way, especially the 5th which was shaky all the way to the end.
Nadal has beaten Tsitsipas in straight sets FOUR times, while Tsitsipas has never done it once.
Tsitsipas is always at Nadal's mercy.....and Nadal doesn't appear to be in a merciful mood.
BTW I don't think Nadal is lacking confidence.....because he's hitting very hard and taking risks.....whereas in 2015 he was hitting softly and safely.
The reason for him losing to Rublev was a combination of rust (7 double-faults and the backhand was error-prone) and the fact that Rublev is a lot younger and athletic enough to run all day with Nadal.
And in Barcelona, Nadal's serve is improving and almost fully back to normal, and his backhand is still error-prone, but I don't see it as a confidence issue.....because Nadal's forehand looks perfectly confident.....and Nadal's forehand has always been the barometer for his confidence.