Even Flavia Pennetta was a tiny bit disappointed that Serena Williams didn't complete the first Grand Slam since 1988 at the U.S. Open.

"Of course," she said hours after she won her first major title in her final chance before retiring — well aware that had Williams accomplished the feat, it would've meant no championship for Pennetta.

She was thrilled for childhood friend Roberta Vinci for her upset of Williams in Friday's semifinals, but Pennetta was like any other tennis fan captivated by the chance to witness a rare achievement.

"Also, I was thinking it was going to be nice to be on court with her, and maybe lose, but for a moment so special for everyone, for her, for history," she said.

Not that Pennetta intended to lose when she thought for a few hours that her opponent in the final might be the 21-time major champion. Asked about the potential matchup after her semifinal win Friday, Pennetta said with a wry smile: "It's going to be amazing for her to do something like that, and it's going to be amazing for me to win this tournament."

She also warned reporters not to count out Vinci, even though her fellow Italian was down a set at the time.

Vinci's victory set off a whole different kind of stress for Pennetta. Suddenly she was the favorite in her first Grand Slam final.

"It was: Now I have more of a chance," Pennetta said Saturday. "But on the other side, I tried not to put in my mind that I HAD to win. I had an upset stomach. I even cried. There was an accumulation of emotion."

She controlled those emotions after a shaky start to beat Vinci in straight sets. Then with her post-match interview about to end, she interjected that she had one more thing to say: Pennetta was retiring.

It was a stunning announcement but not a rash decision to go out on top — she had resolved a month earlier to step away from the game at the end of the season.

The 33-year-old was OK that her career was going to end without a major title. Her trainer asked before the U.S. Open if she thought she could still win a Grand Slam championship and Pennetta said no.

"Now they're laughing so much," Pennetta said Saturday about her team.

They've been teasing her: "You have a double personality for sure."

Her fiance, fellow player Fabio Fognini, said he thought she should stay on tour but respected her decision.

"She's hard-headed, very determined in anything she does," he said.

Fognini, who lost in the fourth round last Sunday, flew back from Italy on Saturday morning to attend the final. He bit his fingernails in the stands at Arthur Ashe Stadium, a nervous spectator in the same venue where he thrilled fans eight days earlier in the most captivating match of this year's U.S. Open before Vinci's upset of Williams.

Down two sets and a break in the third round to 14-time major champion Rafael Nadal, Fognini made brilliant shot after brilliant shot to win in a pulsating fifth set. Then his fiancee went out and earned an even bigger victory for Italy.

An Italian woman had never won a major singles title before Francesca Schiavone at the 2010 French Open. Her breakthrough seemed to inspire both Pennetta and Vinci to late-career successes.

Italy had never won a Fed Cup championship before 2006. Behind Schiavone, Pennetta, Vinci and Sara Errani, the country has four of the last nine.

Errani reached the French Open final in 2012, then Pennetta and Vinci made their debuts in a major title match at this U.S. Open.

"It's amazing that the four of us play final in Grand Slams," Pennetta said. "We have so many good things together. We spend so much time together."

The four went to dinner before the start of a tournament that would end in the first all-Italian major women's final. Fognini is already looking forward to walking the hallways inside Ashe during next year's U.S. Open, where photos of past champions line the walls — and Pennetta's picture will join them.