Novak Djokovic has not played any events leading up to the US Open electing to play himself into form at the event. It's a tactic he employed before and it usually works for him. After another win at the US Open he assessed how it was going:
"Great performance. Definitely better than the first-round match. Obviously I'm very pleased with the way I came out on the court. I served very well, I found the rhythm on the serve. It was important I came up with the goods."
Djokovic caught a lucky break when Griekspoor defeated Struff in the previous round taking down the German in 5 sets. The Dutch player arrived somewhat tired to this match and Novak exploited that:
"I made him play. I saw him [for the] first time playing in his first-round match a couple days ago with Struff, saw he was serving really well, so I knew that one of the biggest keys was my return, trying to make him play, trying to make him move. He's not the greatest mover on the court. I tried to give him always a different look."
Djokovic will face Kei Nishikori next and the Serbian has a 17-2 record against him. The last defeat against Nishikori came in 2014 at the US Open which could make this match interesting.