2019 was Federer's last healthy year on tour. He played some amazing tennis for a 38 year old man! From Dubai all the way through Wimbledon Roger looked very similar to his 2017 level.
Honestly, I thought Federer had a good shot at making the final in AO 2019. He was still in pretty good form overall in terms of health and tactics. Tsitsipas played a very good match and Federer at times cracked on opportunities that cost him in a match with small margins. Had Federer made it through Tsitsipas, I would think he would be the heavy favorite over Nadal in the SF.
Evans was a qualifier here so I expected this to be an easy one for Fed given that he was the 2 time defending champ even if my hunch was that Roger would not defend this title (but I did not expect the loss to come against Tsitsipas).
I'm not sure, but I'm thinking that hose deep-set eyes of Federer's might have somewhat limited glare from sunlight or bright indoor lights. But he himself credited his superior coordination, and that would be a really great advantage in tennis. But the right character and mentality for tennis would have to be of equal or greater value than anything physical.