World No. 1 Novak Djokovic and reigning champion Agnieszka Radwanska earned contrasting wins in the early stages of the China Open on Tuesday.

Djokovic, playing his first match since losing the U.S. Open final to Andy Murray last month, was made to sweat by Germany's Michael Berrer, ranked 123 in the world, but prevailed 6-1, (3)6-7, 6-2 in the first round.

The Serbian star meets Carlos Berlocq of Argentina in round two.

Elsewhere, third seed Jo-Wilfried Tsonga snatched a comeback victory over Uzbekistan’s Denis Istomin 4-6, 6-1, 7-6(3).

The Frenchman next meets world No. 43 Nikolay Davydenko, who was victorious in the all-Russian first-rounder against qualifier Alex Bogomolov 7-5, 6-1.

The only seeded man to fall Tuesday was German veteran Tommy Haas, seeded seven.

The 34 year old had serious serving problems to make 10 double errors in surrendering to Russia’s Mikhail Youzhny 6-4, 4-6, 6-2.

Youzhny plays Kevin Anderson of South Africa, ranked 36 in the world, in round two.

In the women’s draw, Tuesday was the day for the second-round clashes, where third seed Radwanska breezed past local wild card Zhang Shuai 6-2, 6-3.

The Polish right-hander will continue the defense of her title against qualifier Lourdes Dominguez Lino. The Spaniard, ranked 64 in the world, beat British youngster Laura Robson 7-5, 6-3.

Eighth seed Sam Stosur suffered a second-round upset to Julia Goerges of Germany. The Australian former U.S Open champion hit 14 double faults in a 7-6(2), 4-6, 7-5 defeat.

In round three, Goerges will face ninth seed Marion Bartoli, who ousted Japanese qualifier Ayumi Morita 6-4, 6-3.

Meanwhile, Chinese star Li Na eased past Japan Open champion Nadia Petrova 6-1, 6-2.

Li, seeded 7, will play local world No. 49 Peng Shuai in round three.