Victoria Azarenka narrowly avoided becoming the first top seed to lose in the French Open first round on Monday as Roger Federer celebrated his 50th straight major with a record-equalling 233rd Grand Slam win.
World number one Azarenka had to come from a set and 4-0 down to defeat Italian world number 105 Alberta Brianti 6-7 (6/8), 6-4, 6-2 and will face German qualifier Dinah Pfizenmaier for a place in the last 32.
But for much of her rollercoaster 2hr 16min battle with 32-year-old Brianti, who had never won a match in four previous main draw appearances at Roland Garros, Azarenka struggled.
Brianti was on the verge of a 5-0 lead in the second set when Azarenka sent down a second serve ace to stay in contention, the point proving to be the significant moment in the tie.
Australian Open champion Azarenka, who finished with 60 unforced errors, came into Roland Garros nursing a shoulder injury and it appeared that she was heading for a shock exit until she reeled off 12 of the last 14 games.
"I started well but my game just collapsed," admitted 22-year-old Azarenka, twice a quarter-finalist in Paris. "I tried to stay concentrated. I don't know how I got out of it."
Meanwhile, defending women's champion Li Na of China advanced to the second round with a 6-2, 6-1 win over Romania's Sorana Cirstea, a quarter-finalist in 2009.
Federer, the 2009 champion and four times runner-up to Rafael Nadal, endured few problems getting past Germany's Tomas Kamke, the world number 78, winning 6-2, 7-5, 6-3.
His win, achieved on a sixth match point, also took him level with Jimmy Connors' record for most Grand Slam match wins of 233.
The 16-time Grand Slam title winner next faces either David Nalbandian of Argentina or Adrian Ungur of Romania.
Federer, seeded three, is scheduled to meet world number one Novak Djokovic in the semi-finals.
Top seed Djokovic kicks off his bid for an historic Grand Slam later on Monday when he tackles Italian claycourter Potito Starace.
The Serb is just seven wins away from becoming only the third man to hold all four majors at the same time.
But the Wimbledon, US Open and Australian Open champion has never made a final in Paris, falling at the semi-finals on three occasions.
Meanwhile, women's 11th seed Vera Zvonareva withdrew from the tournament suffering from a right shoulder injury.
Kazakhstan's Sesil Karatantcheva, a 'lucky loser' from qualifying, took her place in the draw and defeated Hungary's Timea Babos.