That was a hard fought win from Federer. But one thing I saw him during the match (especially in the 5th set tiebreaker) and after he won the match, I think he was ready to "give in" meaning he just wanted to go home and see his family. He is definitely relieved that he won the match, but at the same time, he probably knows deep down his body will not able to survive to win the Australian Open. He looked lifeless especially towards the end of the match.
This type of match reminds me of Nadal in the 2018 US Open in which Nadal won those hard-fought matches (Khachanov, Basilashvili, and Thiem) but he had to pay a dear price physically. I do think Federer will able to recover from this (reach the SF) but he probably won't be the same physically.
It is why it is important for the Big Three at this point their career to be physically fresh as possible so they can maximize their chances winning a slam. Even Djokovic needs some physical recuperation because he is 32.5 years old.