A day after insisting she was still the best player in the world despite falling from No. 1 in the rankings, Serena Williams lost to Patty Schnyder in her first match at the Italian Open late Tuesday night.

Williams, playing her first match in almost a month, appeared to be moving with difficulty at times during her 6-2, 2-6, 6-1 loss on clay at Foro Italico.

"We all know who the real No. 1 is," Williams said on Monday. "Quite frankly, I'm the best in the world."

Earlier, Dinara Safina, the player who overtook the top spot from Williams, bumped off Virginie Razzano of France 7-6 (1), 6-1. Defending champion Jelena Jankovic and French Open champion Ana Ivanovic all advanced to the third round, as play was disrupted by rain and went late into the night.

"It's not luck," Safina said on Monday. "Nobody gave it to me - I proved it. I played two Grand Slam finals and last year I won four titles ... so I think I belong to this, because this doesn't come out of sky."

Grand Slam titles

The 23-year-old Safina, who lost to Serena in the Australian Open final, said Williams was entitled to claim to be the real No. 1 because she has won 10 Grand Slam titles.

"But she's also older than me, so she has more experience than me," Safina said. "So let's see when I'm her age how many titles I'm going to have and then we can say."

Williams was broken twice in the first set, came back in the second set but the 2002 champion went down 5-0 in the third and fell for the first time before the quarter-finals in nine visits to Rome. Williams also lost three consecutive tour matches for the first time since the end of 2007.

Schnyder, ranked 20th, won for the fourth time in 12 matches with Williams and second time in Rome.

Safina overcame a shaky start, allowing Razzano to take the initiative for most of the first set, but she dominated the tiebreaker and then kept the momentum with an early break in the second set before winning the last four games.

She complained that the rain before the match had made the court damp and dangerous to play on.

"I was just so angry, because you can get injured," said the Russian, who fell in the first set as she rushed to the net to retrieve a drop shot, but couldn't slide. "It's soft and you're afraid to play."

She said tournament organisers should "have a little bit of respect to us as the players."

Earlier, Jankovic began her defense of the Rome title with a 6-3, 7-6 (6) win over Gisela Dulko. The match was suspended for about 3-1/2 hours due to rain.

"It's difficult when it rains and then you have to stop and you know, focus again and start," Jankovic said.