Serena Williams has many great ingredients to her game, but invincibility is not among them.

She had publicly suggested that it might be possible to go through 2003 undefeated, winning every Grand Slam event and a whole lot more.

But the notion was just ridiculous, since even the world's best sportsmen have off-days, the sort which Williams suffered on Sunday when she lost to Justine Henin-Hardenne of Belgium in the Family Circle Cup final.

Second seed Henin-Hardenne of Belgium handed the top-ranked American her first defeat of the year after 21 straight wins, running out a 6-3 6-4 winner in the claycourt event.

"I wasn't as involved as you guys were," Williams told reporters when asked about the unbeaten run.

"Sometimes you need to lose. I set my goals for the sky. That doesn't necessarily mean I get them."

Since a loss to another Belgian, Kim Clijsters, in the final of the year-ending WTA Championship in Los Angeles last November, Williams won three titles, including her fourth straight Grand Slam crown at the Australian Open in January.

She was 21-0 on the WTA Tour and undefeated in 25 total matches.

"My whole game was 9,000 notches down," said Williams after her setback.

"I can't be on my top level every day, and today's just one of those days I just didn't play well.

"I didn't serve well, I didn't return well, I didn't hit well."

Feeling she was being denied some credit, Henin-Hardenne countered: "But why did she do all these mistakes?

"Maybe because everything was coming back and I was running all over the court and she did not have any solutions to her problems.

"She did a lot of unforced errors, but I think that I put on her a lot of pressure."

Henin-Hardenne claimed her second title of the year and eighth of her career, earning £120,000.

The winner at Dubai in February, she notched just her second win over Williams in six meetings, but her second on clay.

"It's still very tough to beat Serena, and today I just kept fighting and finally won the match," said Henin-Hardenne, who lost to Venus Williams in the 2001 Wimbledon final.

"I agree that for me on clay court it's much easier than on the other surfaces because we could see that I had much more time to organise my game, and it's not the same power on clay."

Williams won the first three games of the match, but Henin-Hardenne ran off a string of six straight games - winning 22 of 25 points at one point during that stretch.

She capitalised on her first set point by nailing an inside-out backhand return of serve for a winner.

"I made way too many errors every time I tried to to hit a ball," a downcast Williams said.

"My forehand, which is my stronger side, I missed.

"It was a little discouraging."

Henin-Hardenne might have been down but she kept the faith that she could win.

"When I was down 3-0 in the first, I can tell you that it was hard to come back in the match," she said.

"But then I just said, 'Okay, play point after point', and I just went all over the court."

Williams started the second set much as she did the first, winning 11 straight points, the first two games of the set and taking a 40-0 lead in the third game.

But Henin-Hardenne got back on track.

She won four straight points before holding her serve and eventually evened the set at 3-3.

"It was the key of the match, or the key of the second set because if I lose this game, two breaks, it's going to be hard against Serena Williams, for sure," Henin-Hardenne said.

Williams, never one to give up, held triumphantly at love to regain the lead at 4-3.

Serving to stay in the match at 4-5, Williams quickly fell down 15-40.

She saved one match point and nearly served an ace to save the second, but a fully extended Henin-Hardenne just blocked the return back over the net, which Williams dumped into the net.

Henin-Hardenne played a strategically brilliant match, consistently changing her pace, spin and depth of her shots.

"She didn't like that I mixed it up a little bit more, and it worked," the 20-year-old Belgian said.

"I did high ball, slice, fast ball, and I think that today I had to do this to win the match."

This was Henin-Hardenne's second career Tier I tournament triumph and her first title in the United States.