I don't think that Serena's pressure to win that USO open was any greater than Nole's pressure to win his 4th in a row in Paris of all places, where he had never won before. I know people were not sold on the fact that he would ever win FO but he did it, despite all of that pressure and the pressure of going for 4 in a row. Even if it was not in the same calendar year, it is the 2nd best thing to happen in tennis, for me, so I am extremely happy about it.
Anyway Nole hinted at being mentally off after that huge FO win so he had his 2 mishaps in the majors this year and can start fresh at attempting to win 4 in a row again (this time in the same year, starting in Australia in 2017). The timing is actually perfect. He just needs to stay injury free (yes, toes, fingers, elbows, shoulders all count here).
He is always fresh, eager and relatively injury free in the first few months of ever season, then it gets complicated as he plays more matches and there is more possibility to get injured and tired mentally and physically. That is what makes it so difficult to always win and get to major finals. I said this last year and I stick to it, I really don't care about how many masters titles he wins, he has plenty of them already, but navigating through the whole season and trying to peak and play his best 4 times a year for the duration of majors, that is a big challenge for anybody. Should be interesting to see what happens.