Oh, Nadia! Oh, Petra! and other highlights of the day

Nadia Petrova has been serving really well lately, and when Petrova serves well, she's a threat. She was a big threat to Maria Sharapova tonight at the U.S. Open, dropping the first set, winning the second, then immediately going up a break in the third. Then it began to rain, and the match had to be suspended. Oh, Nadia. It seemed obvious that a rain delay could only benefit Sharapova, and indeed it did. She returned to the court and broke Petrova right off, then raised her game to such a level that even Petrova's serve couldn't save her anymore. Sharapova won their round of 16 match 6-1, 4-6, 6-4.

Sharapova's intensity in the third set probably could have powered a large building filled with electronic equipment. But consider this: The Russian's intensity was nothing compared with the show put on by Marion Bartoli in her match against U.S. Open Series winner Petra Kvitova. A few weeks ago, in Montreal, Bartoli won only two games against Kvitova, and said later that there was absolutely nothing she could do when Kvitova played at that level.

Indeed, Kvitova won tonight's first set 6-1. It looked like there might be a repeat of the Rogers Cup beat-down, but then things changed dramatically. Kvitova began making unforced errors, hinting that she was about to turn in one of her "off" second sets. She did; Bartoli won the second set 6-2. The final set was not only a meltdown for Kvitova--it was a kind of Mad Frenchwoman opera for Bartoli. The 11th seed more or less went crazy on Kvitova, putting on a serving clinic, yelling, fist-pumping, and shadow-swinging up a storm. It was a huge performance in every way. The Czech player did not win a game.

None of us knows for sure why Kvitova played in Montreal, Cincinnati and New Haven, though I suspect she did it in order to adapt to the humid conditions, which generally trigger asthmatic attacks in her when she plays on this continent. The good news is that she won two of those tournaments, reached the semifinals in the other, and won the U.S. Open Series. The bad news is that she played a lot of matches just before coming to the U.S. Open. One can't help but wonder "What was she thinking?"

But such is the unpredictable career of Petra Kvitova. At least she doesn't have to play Sharapova again. That job goes to Bartoli.

Not surprisingly, top seed Victoria Azarenka won her round of 16 match in straight sets. She defeated Anna Tatishvili 6-2, 6-2, but the match was certainly better than the score indicates.

Defending champion Sam Stosur--remember her?--ended the run of Laura Robson today. I was wrong, too: Robson did let the occasion get to her, which was part of her undoing. Stosur won 6-4, 6-4, but what drama! In the first set, Robson went up an early break, but made enough unforced errors to get broken back. She had break opportunities at 4-all, but couldn't convert them, and was broken at 4-5.

Robson went down 1-4 in the second set, and looked like she might get into even bigger trouble, but two really good forehand shots and a good second serve helped her hold. Serving at 2-5, Robson saved two match points, but double-faulted on two game points. She also hit a volley into the net. But she relied on her big serve to save three more match points before she was finally able to hold.

By this time, Robson's confidence had returned. When Stosur served for the match at 5-3, the British upset star saved two more match points and broke her. Robson then saved yet another match point on her own serve, but Stosur finally won the match on her ninth match point. The defending champion thrived on this kind of high drama at last year's Open, so who knows what might happen? Just like last year, Stosur's matches aren't being given much fanfare, and that's probably okay with her.

Defending champions Melanie Oudin and Jack Sock, after winning a thrilling first round of mixed doubles, went out today to Sania Mirza and Colin Fleming, who beat them 6-4, 7-6. Also going out were top doubles seeds Liezel Huber and Lisa Raymond, who lost to Hsieh Su-Wei and Anabel Medina Garrigues. 2nd seeds Sara Errani and Roberta Vinci advanced, as did 3rd seeds Andrea Hlavackova and Lucie Hradecka.