The Spaniard revealed he wanted to watch Japan play Argentina in a soccer friendly in Saitama -- more than an hour's drive away -- in the evening and catch up with his friend Lionel Messi.
Frenchman Gael Monfils ousted second seed Andy Roddick 7-6, 4-6, 7-6 in a pulsating quarterfinal earlier in the day.
Nadal came out with all guns blazing and after safely pocketing the first set the Spaniard blitzed through the second to win in 72 minutes. Nadal plays Viktor Troicki next after the Serbian's 6-2, 3-6, 6-4 win over Spain's Guillermo Garcia-Lopez.
Roddick saved three match points but Monfils superbly threaded a forehand down the line on his fourth chance in the tiebreak, triggering chest-thumping celebrations. Monfils will play Czech Radek Stepanek in the semifinals after Finland's Jarkko Nieminen pulled out with a fever before a ball was hit.
Wozniacki in semis
World number one Caroline Wozniacki began life at the top with an injury scare on Friday, while champion Novak Djokovic said players should have access to oxygen tanks on court after yet another smoggy day in Beijing.
Ecstasy turned to agony for Wozniacki less than 24 hours after she was crowned world number one when she crumpled to the ground clutching her left knee in tears while leading Serbia's Ana Ivanovic 7-6, 3-1.
The 20-year-old overstretched as she smashed a backhanded return but after taking an injury time out to get her knee strapped, she showed her champion's instinct to reach the semifinals by shunting aside Ivanovic 7-6, 6-4. Djokovic beat Frenchman Gilles Simon 6-3, 6-2.
Robin Soderling and Nikolay Davydenko, both slumped out. Soderling was beaten 6-2, 6-4 by Spain's David Ferrer and Davydenko handed a 7-6, 6-4 defeat by lofty American John Isner. Unseeded Isner now faces Djokovic.
Francesca Schiavone was thumped 6-0, 6-2 by second seed Vera Zvonareva. China's Li Na, seeded ninth, silenced Latvian Anastasija Sevastova 7-6, 6-3 and now faces the in-form Zvonareva in Saturday's semifinal. Israel's Shahar Peer overcame Switzerland's Timea Bacsinszky 7-6, 6-4.