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 on Wednesday.
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 off points.
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, S.C., and Madrid - plus two victories in Fed Cup.
By winning the Madrid Open on Sunday, Federer moved past Nadal to No. 2 for the first time since March, 2011.
"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 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 next plays former No. 1 Juan Carlos Ferrero, the 2001 Rome champion.
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.
While his ranking improved to No. 2, Federer is seeded No. 3 this week.
Federer considered skipped 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.
"I am tired with all the matches that I am playing on clay court(s) and I have some problems with my back,'' said Radwanska, adding she'll probably play in Brussels next week. "But I still have some more matches before Paris.''
Three seeds advanced.
No. 5 Samantha Stosur knocked out Sara Errani of Italy 6-3, 7-5; 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.
Later, Nadal begins his pursuit of a sixth Rome title against 28th-ranked Florian Mayer, who beat the Spaniard in their only previous meeting. Both Serena and Venus Williams will play, along with top-ranked Victoria Azarenka.