Ddn't see all of the match but from what I could tell the first 2 sets were very tight (well, they both went to tie-breakers so that's a bit obvious). Murray seemed the better player for most of the first 2 sets but his level noticeably started to drop towards the end of the 2nd. In the 2nd set breaker, there was a bizarre incident with a falling feather that I think he let distract him as he was about to serve at 2-2 because he then double-faulted to hand Djokovic the mini-break which he then held onto.
After Djokovic had levelled at 1 set all, Murray took an MTO to get his foot bandaged. It looked very blistered. After that, his movement noticeably slowed and seemed hampered and his groundstrokes declined in quality. His serve held good for the most part but eventually that too cracked and Djokovic got the vital break in the 7th game of the 3rd set. He never looked back after that and upped his level to take the 4th and the match.
In short, Murray had definite chances in the first 2 sets but his movement and level rapidly deteriorated after that. In a reversal of the US Open final, Djokovic definitely outlasted Murray in the fitness stakes. With these 2, it very often becomes a test of stamina in the end. Murray won the last contest, Djokovic won this one. Deservedly so.
"I have to apologise because I clearly pushed Roger so hard on Thursday!" (Andy Murray on why Federer couldn't play the WTF final).