Rome - French ingenue Alize Cornet vaulted into her fourth career clay-court semi-final as Serena Williams withdrew prior to their Friday match at the WTA Rome Masters with a sore back. The American's camp said she hit only a few shots in warm-up on a practice court prior to the blockage.
"It happened all of a sudden in practice," said Williams. "I went for a shot and then my back got a little stuck.
"I'm just going to keep training for Roland Garros and get ready for that. I'm in really good form, so I'm going to be going in with a couple wins under my belt.
"I tried to wait until the last possible moment to see if I could play."
Williams retired during matches three times in 2007, handing over a total of ten matches to opponents since 2001. She last quit against Anna Chakvetadze at the season-ending championships last November in Madrid.
The Americanbeat number 34 Cornet in their only other meeting, last month in the Charleston semis on American green clay.
Cornet, an 18-year-old hope, will play on Saturday against off-the-boil sixth seed Chakvetadze.
The ragged Russian struggled into the final four with an unappetising 6-2, 3-6, 6-1, win over Bulgarian Tsvetana Pironkova.
"I don't know what happened, I felt like I was playing against myself," said the sixth seed after winning a low-standard contest marred by a combined 87 unforced errors.
The win in just under two hours end the giant-killing week of the 20-year-old Pironkova, who beat top seed Ana Ivanovic in the second round.
The Bulgarian ranked 64 has lifted her level at the Foro Italico after failing to win out of qualifying rounds three times this season.
Chakvetadze said she was troubled by a right shoulder, a complaint which also bothered her opponent.
The Russian took treatment but said that she felt a chill during that break which compromised her second set. "I was not there in the second set," she confessed. "I'm just glad I got through this match.
"In the second set I didn't feel that well and the shoulder was still bothering me."
