Shanghai, China (My Sportsbook) - Australian Open champion Rafael Nadal and last week's Beijing titlist Novak Djokovic posted second-round wins, while injured U.S. Open champ Juan Martin del Potro exited the $5.25 million Shanghai ATP Masters on Wednesday.

The top-seeded and former world No. 1 Nadal was tested in a 6-2, 6-7 (4-7), 6-4 victory over American James Blake on the hardcourts at Qi Zhong Tennis Center, the former site of the ATP's Tennis Masters Cup. Blake also took Nadal to three sets before succumbing to the powerful Spaniard last week in Beijing.

The six-time major champion Nadal snuck past Blake in 2 hours, 12 minutes on Wednesday.

Nadal's third-round opponent on Thursday will be 14th-seeded fellow Spaniard Tommy Robredo.

A second-seeded Djokovic remained hot with a 6-3, 6-1 pasting of Italian qualifier Fabio Fognini on Day 4. The Serbian Djokovic is fresh off his title in Beijing.

Djokovic will encounter German Rainer Schuettler on Thursday.

A third-seeded del Potro, meanwhile, gave way to Austrian Jurgen Melzer and a right wrist injury on Day 4. The lefthanded Melzer was leading the U.S. Open champ 7-5, 2-1 when del Potro quit.

Del Potro is now 0-2 since stunning Roger Federer in last month's U.S. Open final, with the other loss coming at the hands of little-known Frenchman Edouard Roger-Vasselin in Tokyo last week.

Fifth-seeded French star Jo-Wilfried Tsonga, like Djokovic, continued a winning streak on Wednesday by dousing Chinese wild card Shao Xuan Zeng 6-3, 6-3. The former Aussie Open runner-up, to Djokovic last year, is fresh off his hardcourt championship last week in Tokyo.

Up next for Tsonga will be rising Swede Robin Soderling. The ninth-seeded French Open runner-up Soderling continued his fine play of late by handling Spaniard Nicolas Almagro 6-4, 7-5.

Another upset came when former Top-10 star Ivan Ljubicic surprised seventh- seeded Spaniard Fernando Verdasco 6-4, 7-6 (8-6).

Eighth-seeded Frenchman Gilles Simon avoided an upset by erasing promising Serb Viktor Troicki 6-3, 6-4, while 11th-seeded French acrobat Gael Monfils doused former top-ranked star Lleyton Hewitt 4-6, 6-4, 6-4.

In other second-round action involving seeds, the aforementioned Robredo overcame German qualifier Florian Mayer 4-6, 7-6 (12-10), 6-4, Schuettler took out No. 15 fellow German Tommy Haas 6-4, retired, and Feliciano Lopez upended 16th-seeded fellow Spaniard David Ferrer 4-6, 7-5, 6-1. Robredo saved three match points against Mayer in order to set-up the meeting with Nadal. Haas retired against Schuettler due to a right shoulder injury.

One other second-rounder saw Czech Tomas Berdych come back to best former world No. 1 Marat Safin 3-6, 6-4, 6-4. This marked the wild card Safin's final match in China, as the big Russian will retire from the ATP World Tour at the end of this 2009 season.

This inaugural event closes out a three-week Asian swing on the ATP and the eventual winner will take home $616,500.