BRINDISI, Italy -- Nineteen Grand Slam titles. Nearly 20 years as a professional. An undefeated record this year. And not one career loss in the Fed Cup.
Wearing red, white and blue, the top-ranked Williams was put to the test as she kicked off her clay season in front of a hostile crowd Saturday. The end result, though, was quite familiar.
"I competed well," the 33-year-old Williams said. "She played very, very well and I stayed in there. I didn't get negative. I stayed positive and just did the best that I could. I've been working really hard my whole life, so maybe it was just experience."
Neither player broke serve in the first set, which was only decided when Giorgi missed two straight forehands to end the tiebreaker.
"My game is very instinctive and I made two key errors," the 23-year-old Giorgi said. "Two errors are not many but it depends when you commit them. In a tiebreak, two points are worth gold. But I have no regrets for how I played."
Williams improved to 19-0 this year and 15-0 for her career in Fed Cup. The only blemish on Williams' 2015 record came when she withdrew before the Indian Wells semifinals last month with a knee injury.
Giorgi was an unexpected choice by captain Corrado Barazzutti for Italy's second singles spot over Brindisi native Flavia Pennetta but she showed surprising poise and was even able to match Williams' power in the opening set.
Giorgi and Williams had 17 winners apiece in the first set -- which lasted more than an hour -- while Williams committed 18 unforced errors to Giorgi's 15.
Unable to impose her game, Williams appeared frustrated and kept shouting "Come on!" to herself in angrier and angrier tones as the first set wore on. Williams consistently applauded, putting one hand to her racket, when Giorgi blasted winners by her, prompting the capacity crowd of 4,000 to break into chants of "I-TAL-IA, I-TAL-IA."
But Williams played solidly in the tiebreaker and Giorgi clipped the top of the net on Williams' first set point.
"It was a great match. Giorgi played great throughout," U.S. captain Mary Joe Fernandez said. "Serena did a good job to really fight and play a solid tiebreak. She served really well in the tiebreak, which I thought was the difference."
In the second set, Williams took control early on.
"I haven't played that many points on the clay so I think that factored a little bit," Williams said. "But it was also that she played really well. She had a great game plan and that's the player she is. She just goes for a lot."
Barazzutti was pleased with the score at the end of the first day.
"I hoped it was going to be 1-1 and that's where we're at," he said.
In Sunday's reverse singles, Williams plays Errani followed by Davis against Giorgi, although Barazzutti will likely substitute Pennetta for Giorgi.
The winner returns to the World Group and can compete for the Fed Cup trophy next year while the loser will be relegated to World Group II.
In other Fed Cup action:
Australia 1, Netherlands 1
Czech Republic 2, France 0
The hosts are one win away from the final against Germany or Russia in November to have a chance of winning their fourth title in five years. France is playing in its first semis since 2007.
Russia 2, Germany 0
The result left Russia needing one win from Sunday's three matches to reach the final and bag a first Fed Cup title since 2008.
With the Czech Republic leading France 2-0 in the other semifinal, there was potential for a rematch of the 2011 final, when the Czechs beat Russia in Moscow.
Information from The Associated Press was used in this report.