No. 1 Serena, No. 2 Halep shocked by Italian vets Vinci, Pennetta

Thoughts on a shocking day of upsets in the U.S. Open women's semifinals: Serena Williams upset by Roberta Vinci, Simona Halep loses to Flavia Pennetta.

NEW YORK – Five quick thoughts from a stunning women’s semifinals at the 2015 U.S. Open.

• What is the sound of 20,000 tennis fans groaning? Well, now we know. Two matches from achieving the Grand Slam, tennis’ answer to the Triple Crown, Serena Williams was strung tighter than her racket and bowed out, astonishingly, to unseeded Roberta Vinci of Italy, 2–6, 6–4, 6–4, one of the great upsets in tennis history. Serena won the first set 6–2, shakily but clearly superior. Then she could scarcely find the court. Plenty will be made of Serena’s nerves and her palpable anxiety. Against a far inferior opponent ranked 43, the World No. 1 made scads of errors, served poorly and moved as if cinderblocks were affixed to her ankles. But credit Vinci. She won the long rallies. She kept her cool while her opponent didn’t. She met the moment, winning the last game for the match of a lifetime. In a word: Wow.

• Roberta Vinci might be the answer to a trivia question (and the least popular woman in New York.) But she is suddenly a match from a highly unlikely title. In her first major singles semifinal, Vinci, 32, played crafty tennis, slicing, dicing, playing angles and overcoming a huge power differential with guile. It’s easy to see why she’s had such a successful career in both singles and doubles. Her pluck and her scything slice were easy on the eyes, and surprisingly effective. She closed out the match with poise. Now she plays for the whole bowl of pasta.

• Brava, Flavia. A mild-to-considerable upset in the first match as Italian veteran Flavia Pennetta reached her first major final, beating Simona Halep with surprising ease, 6–1, 6–3 in 59 minutes. Pennetta essentially out-Halep-ed Halep, defending well and deploying a surprising amount of offense. She won the first set handily, all the while betraying a smile that said: I’m 33 years old and damn if I’m not going to enjoy this. Halep found the range in the second set and took 3-1 lead. Pennetta withstood this, gathered herself and ran off the next five games, hitting with accuracy (23 winners) and allowing Halep to miss (23 errors.) Pennetta gleefully admitted that Halep was hardly at her best. Who cares? She’s in the final.

Roberta Vinci upsets Serena Williams in U.S. Open semifinals

• What a bittersweet event for Simona Halep. The second seed won the match of the tournament, beating Victoria Azarenka in a spellbinding quarterfinal. In reaching the semifinals, she turned in her best Slam in a year and essentially salvaged her 2015. She was a match away from meeting Serena Williams in the final, a rematch of the Cincy final three weeks ago and a showdown between No. 1 and No. 2. Then, against a lesser opponent, Halep came out flatter than the court itself. Whether it was the occasion, or the nagging thigh injury or simply an off-day, it was an awfully dodgy performance. Halep had certified herself as a top player. But after her vacant performance today, she must be asking herself some uncomfortable questions.

• The tournament began with a dominant, prominent storyline: will Serena close out the calendar Grand Slam, the most formidable feat in tennis, an achievement unseen since 1988? The conventional wisdom: “The player with the best chance of beating Serena Williams is Serena Williams.” Sadly, that’s what happened today. Perspective: this is still one of the most dominant seasons in WTA history. But what a disappointment. We’ve had seeds crashing out. We’ve had drones cashing into the stands. We’ve had head injuries. We’ve had still another Venus-Serena match. Today we had the biggest upset imaginable. Now it's Roberta Vinci versus Flavia Pennetta for history. Ah, sports. See you tomorrow.