By ANDREW DAMPF AP Sports Writer ROME (AP) -- Fresh off a title in Madrid and back at No. 2 in the rankings, Roger Federer defeated Carlos Berlocq 6-3, 6-4 in his opening match at the Italian Open yesterday. Seeking to win one of only three Masters 1000 events he's never claimed, Federer dealt with the swirling wind inside the 10,500-seat stadium at the Foro Italico, coming to the net often to finish points. Rafael Nadal, who was replaced by Federer at No. 2 with his Madrid Open victory Sunday, beat Florian Mayer 6-1, 7-5 to avenge a defeat in his only previous meeting with the 28th-ranked German. Federer said his ranking isn't that important. "I look at the big picture and what is important to me is just to be in the top 10 and if I am No. 2 or not at the French Open doesn't change anything, and it doesn't change anything for Rafa," Federer said. "That I was able to win Madrid was amazing, and that is what I look at right now -- not the rankings." Federer next plays former No. 1 Juan Carlos Ferrero, the 2001 Rome champion. In women's play, Serena Williams rallied past Nadia Petrova of Russia 4-6, 6-2, 6-3 to extend her winning streak to 15 matches. She's won titles in Charleston, SC, and Madrid - plus two victories in Fed Cup. Serena's sister, Venus Williams, had an easier time reaching the third round, eliminating Ekaterina Makarova of Russia 7-6 (7), 6-1. Considering all the tennis Serena Williams has played during her streak, she didn't have much time after finishing her first-round win over Galina Voskoboeva near midnight Tuesday. "It wasn't that easy. It was a quick turnaround," Serena said. "When I saw the schedule, I said 'Oh my God, are you serious?' That's life. You just have to be able to adjust and make the best of it and so I was really happy to come through today." However, Serena appeared to struggle with her back at times. "Everyone has aches and pains here and there and today I felt it a lot because I have been playing a lot and practicing even more," she said. Williams next faces fifth-seeded Sam Stosur, who defeated Sara Errani 6-3, 7-5. Federer won 18 of 23 points at the net and held a 24-13 edge in winners against the 38th-ranked Berlocq in their first meeting. Federer has reached the final twice in Rome, losing to Felix Mantilla in 2003 and to Rafael Nadal in a fifth-set tiebreaker in 2006. Federer considered skipping this tournament to stay fresh after playing a full week in Madrid, but said he decided to play "this morning after practice." With the top eight seeds getting first-round byes, it gave him an extra day off. "At least here we have two days off, which can be a lifesaver," he said. "I don't think I would have played this tournament if I would have had one day off." In other matches, 14th-seeded Juan Monaco cruised past Radek Stepanek of the Czech Republic 6-4, 6-2; and Marcel Granollers of Spain eliminated Italian wild card Fabio Fognini 6-3, 6-4. There were several upsets in the women's tournament, with No. 3 Agnieszka Radwanska, No. 6 Caroline Wozniacki and No. 7 Marion Bartoli each losing. Radwanska was beaten by 28th-ranked Petra Cetkovska of the Czech Republic 6-4, 4-6, 6-1; Wozniacki retired with upper respiratory illness while trailing 6-4, 4-0 to Anabel Medina Garrigues of Spain; and Bartoli was eliminated 6-3, 6-1 by Julia Goerges of Germany. Also, French Open winner Li Na of China beat Iveta Benesova of the Czech Republic 6-1, 7-5; and 12th-seeded Angelique Kerber of Germany eliminated Vania King of the United States 6-3, 6-2. Former French Open winner Ana Ivanovic routed Spanish qualifier Silvia Soler-Espinosa 6-2, 6-1 to set up a matchup with No. 2 Maria Sharapova.