AP Sports Writer
ROME (AP) -- Back pain forced Andy Murray to retire midway through his second-round match at the Italian Open on Wednesday. He may have to sit out the French Open, too.
Rafael Nadal began his bid for a seventh Rome title by cruising past local hope Fognini of Italy 6-1, 6-3 in just 61 minutes, and two-time defending champion Maria Sharapova eased past Spanish qualifier Garbine Muguruza 6-2, 6-2.
Meanwhile, rising Polish player Jerzy Janowicz upset eighth-seeded Jo-Wilfried Tsonga 6-4, 7-6 (5) then celebrated by ripping his shirt apart, showing off his muscular physique.
Murray, who was celebrating his 26th birthday, walked off the court after winning the second set against Spanish opponent Marcel Granollers.
"I have an issue with my lower back," Murray said. "It's been an issue for a while."
Murray took a long injury break early in the second set, getting his left thigh and lower back massaged.
Granollers won the first set 6-3 and Murray won the second 7-6 (5).
This tournament is a key clay-court warm-up for Roland Garros, the year's second Grand Slam, which starts on May 26.
"I would be very surprised if I was playing in Paris," Murray said. "I need to make a plan as to what I do. I'll chat with the guys tonight and make a plan for the next few days then make a decision on Paris after the next five days.
Murray called for the trainer while trailing 2-1 in the second set. He then lost the next two games to trail 4-1 before battling back to force a tiebreaker.
"I want to make sure it goes away," Murray added. "It's been a problem since the end of 2011 but it got bad during last year's clay season."
Nadal will next face Latvian qualifier Ernests Gulbis, who reached the semifinals in 2010.
Gulbis routed Viktor Troicki of Serbia 6-1, 6-1. Early in the second set during an argument over a line call with the chair umpire, Troicki dragged a cameraman out onto the court to shoot the ball mark.
Sharapova now meets 16th-seeded Sloane Stephens of the United States, who rallied past Kiki Bertens of the Netherlands 4-6, 6-3, 6-2.
Stephens reached the Australian Open semifinals in January with a win over Serena Williams.
"She's been climbing up against the rankings," Sharapova said. "I haven't played against her in a while. I'm excited about that matchup."
Earlier, the 24th-ranked Janowicz improved his record against top-10 opponents to 3-5, having closed last year by reaching the Paris Masters final as a qualifier, beating Murray and Janko Tipsarevic along the way. The 22-year-old Janowicz is one of only five players under the age of 24 in the top 40.
After beating Tsonga with a forehand passing shot up the line on match point, Janowicz tore his shirt into pieces and tossed it to the crowd.
"I was really happy, especially because I didn't get off to a good start to the season and I was sick," said Janowicz, who has been bothered by ear, nose and throat infections. "Now I'm healthy."
Last week's Madrid Open runner-up Stanislas Wawrinka withdrew before his match against Alexander Dolgopolov with a right leg injury. Dolgopolov will next face top-ranked Novak Djokovic.
In a rough day for seeded players, Jeremy Chardy of France upset No. 16 Kei Nishikori of Japan 6-4, 6-1.
In the women's tournament, last year's runner-up Li Na beat fellow Chinese player Zheng Jie 6-3, 6-1; seventh-seeded Sara Errani battled past Christina McHale of the United States 7-5, 5-7, 6-2; and 12th-seeded Maria Kirilenko eliminated Varvara Lepchenko of the United States 6-3, 6-1.
Also, 13th-seeded Roberta Vinci beat wild card and fellow Italian Nastassja Burnett 6-1, 6-4; 14th-seeded Dominika Cibulkova rallied past Melanie Oudin of the United States 5-7, 6-1, 6-3; and two-time champion Jelena Jankovic routed fellow Serb Bojana Jovanovski 6-2, 6-0.
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