His conditioning doesn't look nearly as good as it did a few years ago. He can't seem to catch his breath in the corner after the middle rounds and while he's fighting he more and more often opens his mouth to take huge breaths whenever he has a little distance. He legs are looking older too. He doesn't have the same bounce he did even just 2 years ago and at times when he seems gassed his legs look pretty worn.
He's getting old and you can see it pretty clearly in the ring. I still think he should be the favorite against any other middleweight in the world and I'm in no way saying he's washed up or punch drunk like so many other fighters are. He is still great and he puts on amazing fights but he isn't who he was physically three years ago or even two years ago. Maybe a part of it is that as you get older making weight gets even harder and he can't do it easily anymore but whatever the cause it is catching up with him.
What I see doesn't have anything to do with his opponents either. If he lost 12 rounds to 0 against David I wouldn't have said it had anything to do with age because he didn't look old in the ring. It's not some excuse at all. You can get beat or dominated and still look like young and spry and ready for whatever happens. Canelo didn't make GGG look old in there, being old did. Even though I thought he still clearly won the fight he seems to be losing more of a step every time he fights. He could have knocked Canelo out in the middle rounds and I would be saying exactly the same thing.