if you search older threads you'll find out. young Novak had all kind of health issues. that's why some guys still call him a Faker. first episode happened at DC and Fed said Nole was faking his injuries. As a Nole fan, I know what he had to go trough. allergies, gluten sh!t, breathing problems, you name it. Fed was very insensitive.
e.i. look at Soda being sick for so long, not being able to play at all. Nadal too. Novak has had legit health issues (I read about it a lot) but Fed was making fun of him at that time.
Novak definitely was not at peak athletic level or health at that time but you are partially wrong and partially right. I think there were moments when he genuinely didn't feel well on court BUT BUT that said, since he was having so many health issues, definitely there were moments when he was feeling ok/fine but losing where he tried to use it as an excuse and call the medical trainer. we know this because there are some infamous matches where he would sit down for a minute when in a bad position in the set and magically start running around perfectly a minute later. he definitely faked some but I do agree that there were some times where he really felt sick