Gilles Simon, Grigor Dimitrov, Madison Keys advance at Rome

Gilles Simon of France took advantage of a few key double-faults by Jack Sock and rallied for a 4-6, 7-6 (2), 6-3 win Monday in the opening round of the Italian Open.

Sock was up a break in the second set until his usual commanding serve deserted him. The 12th-seeded Simon quickly leveled the set and then jumped out to a 4-0 lead in the tiebreaker with the help of two double-faults by Sock.

Simon, who has won 12 ATP titles in his career, broke late in the third and closed it out at love in the final game.

"I had a tough time finding my game," Simon said. "If I play like that again I'll be out."

Sock, a 22-year-old American ranked a career-high 33rd this week, appeared to lose energy as the match wore on and couldn't deal with Simon's consistency -- committing twice as many unforced errors as the Frenchman (48-24).

"He serves like (Andy) Roddick and his forehand is like (Rafael) Nadal's," Simon said. "If he works on his other shots he could improve a lot."

With the temperature at the Foro Italico soaring above 25 degrees Celsius (nearly 80 Fahrenheit), fitness was key on the red clay courts.

Tenth-seeded Grigor Dimitrov also played cleanly in a 6-3, 7-6 (4) win over Jerzy Janowicz of Poland. Dimitrov had only 11 unforced errors to Janowicz's 31. A semifinalist last year, Dimitrov improved to 9-3 on clay this year.

John Isner, another big-serving American who is seeded 16th, eliminated Joao Sousa of Portugal 7-5, 6-3, and Philipp Kohlschreiber of Germany beat Donald Young of the United States 6-4, 6-1.

Fabio Fognini, Italy's highest-ranked male at No. 31, won a night match over American opponent Steve Johnson 7-6 (0), 6-3.

Fognini produced a shot through his legs early on, although he lost the point. He also bounced his racket on the ground in frustration at the start of the second set but for the most part was able to tame his nerves -- and Johnson.

"I've always had a hard time here so I'm pleased," said Fognini, who has never been past the second round in Rome. "This is a small step forward."

Fognini faces Dimitrov next.

Also on Campo Centrale -- the main stadium -- 13th-seeded Sara Errani, last year's runner-up, used her consistency to wear down Slovakian veteran Daniela Hantuchova 6-4, 7-6 (4).

Errani produced 16 winners and 16 unforced errors while Hantuchova made 43 winners and 41 unforced errors.

In other women's play, Venus Williams, the 1999 Rome champion, beat Czech qualifier and teenager Katerina Siniakova 6-2, 6-2; and 15th-seeded Madison Keys defeated Madison Brengle 6-2, 6-4.

Also, Swiss player Timea Bacsinszky upset 11th-seeded Karolina Pliskova 6-4, 6-0 and improved to 26-5 this year; and Anastasia Pavlyuchenkova of Russia beat Sam Stosur of Australia 6-4, 7-5.

Former Wimbledon finalist Sabine Lisicki beat Sloane Stephens of the United States 6-4, 6-1, and American qualifier Christina McHale overcame Barbora Strycova of the Czech Republic 7-6 (5), 6-1.

In a matchup of two Italian wild cards, Karin Knapp beat 2010 French Open champion Francesca Schiavone 6-4, 6-1.

The Italian Open is the last big warm-up tournament for Roland Garros, which starts May 24.