By Iain Rogers
"Sometimes you run into a player who's red hot and they don't miss," Williams, who will climb up to number two in the rankings on Monday behind her sister Serena, told a news conference.
"I hit hard, Serena hits hard but Aravane hits hard every shot," she said, before adding a note of caution for the young pretender. "But I think there is a difference when you're not supposed to win, you hit hard and then, when you become the favorite you have to understand how to deal with that pressure every week."
Rezai, who beat world number four Jelena Jankovic in the quarter-finals, belts the ball down and won five straight games on the clay in a half-empty Magic Box arena to seal victory.
The silver sliding roof was open to the blue sky and sunshine and the players' grunts and squeals of effort echoed around the stands.
After racing through the first set, Rezai fell 5-2 behind in the second before conjuring up some inspired play as sparkling as her black and gold dress.
"I have a good shot but I had a tactical plan and it worked very well today," she said.
"It's a family characteristic to fight on the court and to be motivated. It's the best week of my career and I'm very happy."
(Editing by Ed Osmond and Pritha Sarkar)