Top-ranked Novak Djokovic wasted a chance to serve out the match and was beaten 2-6, 7-5, 6-4 by sixth-seeded Tomas Berdych in the Italian Open quarterfinals on Friday.
It's the second consecutive week that Djokovic has struggled, having also lost to Grigor Dimitrov in the second round of the Madrid Open, where he was bothered by a right ankle injury.
Djokovic said he had been playing pain free this week. Still, he will need to get his game in shape in a hurry with the French Open less than 10 days away. Roland Garros begins May 26.
Djokovic served for the second set at 5-3 but Berdych ripped a backhand winner that landed on the line on his first break point and won the final four games of the set.
Six-time champion Rafael Nadal overcame one of the worst opening sets of his career to edge latvian qualifier Ernests Gulbis 1-6, 7-5, 6-4 on Thursday and reach the Italian Open quarterfinals.
Nadal's performance, and sometimes sluggish movement on the court, raised questions about whether he will be able to successfully defend his title at the French Open. The year's second Grand Slam starts in 10 days.
Nadal will next face fourth-seeded David Ferrer, who advanced when Philipp Kohlschreiber of Germany withdrew because of dizziness. Second-seeded Roger Federer breezed by Gilles Simon of France 6-1, 6-2.
Nadal, however, was far from his best, especially in the first set, in which Gulbis took a 5-0 lead and even had a point to close out the set at love.
But Nadal, who has reached the final in all seven tournaments he has played since returning to the circuit in February from a seven-month break because of a left knee injury, eventually began to win the longer points while the carefree Gulbis started to commit more errors.
Williams extends winning streak to 22
Serena Williams is on the longest winning streak of her career. And she feels better than ever at age 31.
The top-ranked American rolled past Spanish opponent Carla Suarez Navarro 6-2, 6-0 Friday to reach the Italian Open semifinals and extend her victory run to 22 matches.
Williams had twice won 21 in a row before, although both of those streaks came a decade ago, in 2002 and 2003.
Martina Navratilova established the longest women's win streak in the Open Era at 74 matches in 1984.
Showing off near-perfect form less than 10 days before the French Open, Williams has dropped just three games in her last two matches. Against the 22nd-ranked Suarez, the American hit winners seemingly at will.
The 15-time Grand Slam winner has also won her previous three tournaments.
Williams will next face either two-time Rome winner Jelena Jankovic or Romanian qualifier Simona Halep, who were playing later on an overcast day at the Foro Italico.
In the other half of the draw, two-time defending champion Maria Sharapova withdrew before her quarterfinal against seventh-seeded Sara Errani due to illness.
Sharapova said he was struggling with an illness she first contracted last week, when she was runner-up to Williams in the Madrid Open, although she showed no problems Thursday as she beat 16th-seeded Sloane Stephens 6-2, 6-1.
The withdrawal means Errani advances to the semifinals. The Italian's opponent will be either third-seeded Victoria Azarenka or ninth-seeded Sam Stosur.
The last Italian to reach the semifinals in this tournament was Raffaella Reggi, who won the 1985 event, which was held in the southern city of Taranto. The French Open begins May 26.