"It was a very good first set," Djokovic told the ATP website (www.atpworldtour.com). "High quality tennis from both of us.
"Obviously it was a huge relief for me to win the first set, and started off the second with a break. That gave me more confidence."
Djokovic will face third seed Andy Murray, who barely broke a sweat in defeating Tomas Berdych 6-1 6-3, for a place in the final.
Nadal, a winner of 14 grand slam titles, suffered a second-round defeat by Dustin Brown at Wimbledon and was ousted in the U.S. Open third round by Fabio Fognini but has enjoyed a resurgence since arriving in China.
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The 29-year-old Spaniard, seeded eighth in Shanghai, reached the final in Beijing last week and needed little more than an hour to breeze past French Open champion Wawrinka, who toiled for close to three hours late on Thursday to get past Marin Cilic.
"Being in the semi-finals is a great result for me," said Nadal. "I hadn't played the semi-finals on hard court all year and now I am playing two weeks in a row in the final rounds.
"That's a big improvement for me. In terms of confidence, in terms of level of tennis, I am playing better. Very happy for that because I am working so hard."
Swiss Wawrinka, who had won his last two matches against Nadal, avoided the ignominy of suffering a bagel in the second set by claiming the sixth game after his opponent had raced to 5-0 on the back of a nine-game winning run.
Nadal, hoping to grab one of the four remaining ATP World Tour Finals spots in London, will next meet Frenchman Jo-Wilfried Tsonga for a place in Sunday's title decider.
Tsonga got the better of South Africa's Kevin Anderson in a gruelling 7-6(6) 5-7 6-4 match between two of the circuit's biggest hitters.
The Frenchman saved three set points during the tiebreaker and secured an early break in the deciding set to carry him through to the last four.
"It is a court that he likes to play on," Nadal said of Tsonga. "The court is quick. He feels comfortable on these surfaces because he has a huge serve, very, very good forehand.
"He's a very competitive player. When he's in the semi-finals it's because he's playing well. So it will be a very tough match."
(Reporting by Sudipto Ganguly in Mumbai; editing by Ed Osmond)
