ROME    -      Serena Williams withdrew from the Italian Open on Tuesday ahead of her second-round match against sister Venus because of a previously injured left knee.

Tournament organizers made the announcement a day after Serena opened her clay-court season with a straight-sets win over Swedish qualifier Rebecca Peterson. “I must withdraw from the Italian Open due to pain in my left knee,” Serena said, according to the WTA website. “I will miss the fans and competition at one of my favorite tournaments.

I’ll be concentrating on rehab and look forward to seeing you all at the French Open and next year in Rome.”

The next tournament on Serena’s schedule is Roland Garros, which starts in less than two weeks. It’s the third straight event that the 37-year-old Serena has exited from due to physical problems. She retired due to a viral illness during her third-round match against Garbine Muguruza in Indian Wells, California; and withdrew with the left knee injury before her third-round match at the Miami Open in March. As a result of this latest withdrawal, Venus advances into the third round via a walkover.

Federer seeks more clay matches in Rome

ROME (Agencies): At 37 and with 20 Grand Slam titles, Roger Federer still gets excited about playing tennis. That’s why he added this week’s Italian Open to his schedule.

“I was in the mood to play,” Federer said Tuesday after a practice session on the Foro Italico’s Campo Centrale. “Would I rather practice or play matches? ... There would be excitement, more excitement than me coming to a practice court in Switzerland. “Honestly, I love to play matches. Regardless of what happens here, I just think it’s good for me to play matches at this stage,” Federer added.

After reaching the Madrid Open quarterfinals last week upon his return to clay after a two-year absence, Federer went to Switzerland. He said the cool weather at home also convinced him to make the trip to Rome. “I felt like playing somewhat maybe more sea level conditions would be good for me,” Federer said.

Federer begins play Wednesday against 75th-ranked Joao Sousa, who saved four match points before beating Frances Tiafoe 6-3, 6-7 (3), 7-6 (4) Tuesday. Federer is in the same half of the draw as eight-time Rome champion Rafael Nadal. “I’m so far away in the draw,” Federer said of a possible semifinal matchup with his longtime rival. “I have other problems first getting there.”

Federer is a four-time runner-up at the Italian Open, which he’s never won, making it one of the few significant trophies he hasn’t claimed. Federer is preparing for the French Open, which starts in less than two weeks. Federer had initially planned to play only in Madrid before Roland Garros. When he announced on Saturday that he was coming to Rome, Italian Open organizers raised prices for remaining tickets to Wednesday’s session.

“I heard some fans clearly were not happy about it. That’s obviously disappointing to hear. They rewarded the fans who bought tickets earlier, which is sort of strange, but OK,” Federer said. “I just really hope it doesn’t take away the fact I’m really happy to be here. ... I’m pumped up to play well. My excitement couldn’t be bigger.”

While he hasn’t won in Rome, Federer has found success in Italy. He won his first career title in Milan in 2001. In the memorable 2006 Italian Open final, Federer lost in a fifth-set tiebreaker to Nadal. “Always enjoyed playing in Italy. It’s probably the country I’ve played the most junior tennis in,” he said. “Coming down from Switzerland to the clay courts was always a logical junior trip. They have very strong junior tournaments here.”

Top Russian skateboarder hit with doping ban

MOSCOW (Agencies): A top Russian skateboarder has been handed a four-year doping ban, just as his sport prepares to make its Olympic debut.

The Russian Anti-Doping Agency says Maxim Kruglov, known as “Mad Maxim,” was punished under a rule against athletes who evade or refuse giving a drug-test sample. The agency didn’t give further details of Kruglov’s actions.

Kruglov was the top-ranked Russian in the World Cup street series last year and was aiming for a place at next year’s Olympics in Tokyo. However, he told Russian sports website Championat last year he clashed with the Russian Skateboarding Federation and was skating independently of its national team.