By Toby Davis
PARIS, June 2 (Reuters) - Ask her to describe the way she plays and Serena Williams has a one-word response - fierce.
She is unlikely to hear a word of disagreement from Roberta Vinci after the Italian was beaten 6-1 6-3 in the fourth round of the French Open on Sunday, a result that keeps Williams on course to win a first Roland Garros title since 2002.
The match hammered home the inescapable truth that there is no substitute for raw power in the modern women's game as Williams, whose array of shots could blow holes in concrete, ably demonstrated by out-muscling the canny Vinci.
The Italian found out that as you head into the second week of a grand slam, you need at least one weapon in your armoury that can put your opponent on the back foot.
As it happens, Williams has a whole arsenal at her disposal and wrapped up victory for the loss of only four games, to take the total she has conceded in the entire tournament to 10.
Asked for a word to describe Vinci, a doubles specialist who relies more on her wiles to stay afloat, Williams replied: "Tricky".
Her own epithet was more emphatic.
It was certainly a fearsome display that she put in to complete her 28th straight victory and underline her title potential.
She coped better with the blustery conditions on Philippe Chatrier Court and broke three times to take the first set.
Vinci, who has won three grand-slam doubles titles with last year's French Open singles finalist Sara Errani, tried to move her opponent around the court to compensate for her lack of firepower but it was ultimately a futile effort.
Although she put up a better fight in the second set, she came up short at crucial moments and lost the last 10 points in a row to succumb in one hour 10 minutes.
A sterner test for Williams is likely to come in the next round as her quarter-final opponent is 2009 champion Svetlana Kuznetsova, who is not seeded at Roland Garros for the first time since 2003 but beat the American when they last played at Roland Garros.
The Russian dropped to 85th in the world after a six-month injury layoff following last year's Wimbledon, but has climbed to 39 and is a walloping baseliner who can crunch winners off both flanks.
"The last time we played here she won, so that will probably get her pumped up and she's on a comeback," Williams said. "She has nothing to lose but everything to gain."
Kuznetsova booked her place in the quarter-finals by outplaying German eighth seed Angelique Kerber 6-4 4-6 6-3.
"She's the best in the world so far. She's been playing unbelievable tennis," Kuznetsova said of Williams. "But I believe that I have my game and my good days, as well. Let's cross fingers I will have a good day that one. She's just a fighter." (Editing by Clare Fallon)