Marcos played brilliantly to come back, but what amazes me is how physically, his body almost gave up in the fifth set, while Agassi, at the age of 36, seemed to still be quite fresh. If Marcos was fitter (or as fit as Agassi) he would have won that match. He had 4 break points while the score was at 4-4 in the fifth set, had he taken one of them, he would have surely won. However, due to cramp, he couldn't move properly.
I have watched quite a few of Baghdatis' matches, and when the matches go the distance, he always seems to struggle physically. In my opinion, if he can get fitter, then he definitely has the potential to win Grand Slams.