Britain's Andy Murray was first to advance into the quarter finals after a tough match against American John Isner. He won the match 6-7, 6-4, 6-4.
Murray says the first set was tough but he felt more in control during the second and third sets.
"Once I was in the rallies, I felt in control in the second and third set. In the first set with some of the rallies, he was able to dictate the points using his forehand well and really going for it. But I did feel in the second and third sets when I could get in the rallies, I was dictating the points. "
In other action,
World Number one Novak Djokovic defeated Spain's Feliciano Lopez 6-3, 6-2 in just over an hour.
Djokovic says he's on a good run at the moment and is feeling confident.
"You can't just expect to win all the time comfortably but I've been doing so for the last week and a half and obviously it's given me more confidence. Every time I come back to the court I feel good and I start off well."
South African Kevin Anderson downed Japan's Kei Nishikori 7-6, 7-6 to knock him out of the competition.
Spain's Rafael Nadal beat Switzerland's Milos Raonic 6-3,7-6.
Czech Tomas Berdych also advanced to the next round after winning his match against France's Gilles Simon 6-3,6-3.
His French compatriot Jo Wilfried Tsonga downed Albert Ramos Vinolas. Ramos had earlier knocked Roger Federer out of the first stage of the tournament.
And there was a shock defeat in men's doubles as defending champions Bob and Mike Bryan failed to progress to the quarter finals being stunned by Robert Farah and Juan Sebastián Cabal 7-6, 6-7, 10-7.
For CRI, I'm Sophie Williams in Shanghai.
