General hercules, that was a huge effort by Anderson. Many say he has choked in the big moments against the better players. But he didn't this time. That was probably his best match ever, and another big effort against a top player since losing to Djokovic at Wimbledon in 5 sets.
Murray seemed tired to me, and the Armstrong court might have not favored him. But Anderson is a few years older, so...
Also Gasquet came away with a big win against Berdych.
And Federer handled the big serving Isnahhhh like he has handled most of the biggest servers he has faced. Focus on his return of serve and holding his own serve, and that usually is enough. Isner lost a tiebreaker 0-7 for the first time in his career of almost 500 tiebreaks. Hard to see how a big server like he is doesn't get a point. Took a bit of luck for that to happen. Still a very mentally exhausting match for 3 sets. Very tight and lasted almost 3 hours.
So here are the quarterfinalists:

Anderson vs. Wawrinka should be interesting. Anderson has taken the last 4 meetings. Stan took the first 3.
Djokovic has Lopez to beat, then either Tsonga or Cilic. I think you are correct.
Somebody will have to blitz Djokovic to win. Nobody is going to outlast him.
I think if anyone, it could be Tsonga. He's been playing well General. He might have a shot.
But yeah, it looks like it could be a Nole - Roger final again, but you never know at the US Open.
Nobody in the Open Era has won the US Open without dropping a set.Neither Tsonga and Federer have dropped a set yet. But it gets tougher from here.
Respectfully,
masterclass