Serena Williams upset in U.S. Open semifinals for 2nd straight year

For the second year in a row, Serena Williams' bid to make history ended with a shocking loss in the U.S. Open to big-serving Karolina Pliskova of the Czech Republic on Thursday night.

A seventh title at Flushing Meadows, which would have been an Open-era record, will have to wait. So will a 23rd Grand Slam championship, another record. And her 3½-year reign at number one in the WTA rankings is over, too, one week shy of what would have been yet another mark.

"Karolina played great today. I think if she had played any less, then maybe I would have had a chance," Williams said. "So I think I wasn't at 100 per cent, but I also think she played well. She deserved to win today."

The 10th-seeded Pliskova began her on-court interview by blurting out that she couldn't believe she'd eliminated Williams to earn a spot in her first major final. 

Another surprising upset

At the 2015 U.S. Open, Williams' bid for a calendar-year Grand Slam ended when she lost in the semifinals to unseeded Roberta Vinci of Italy in one of the biggest surprises in tennis history. This one goes pretty high on the list, too.

This was the 33rd major semifinal of Williams' career, and the first for Pliskova, who beat the 34-year-old American's older sister Venus in the fourth round after staving off a match point. Pliskova is only the fourth woman to beat both Williams siblings during the same Slam.

"Obviously, the match with Venus helped me ... not only with the game, but also with the crowd," Pliskova said. "Was my first match on center court."

And to think: The 24-year-old Pliskova had never been past the third round in 17 previous appearances at majors.

One more to go

Pliskova, meanwhile, is now one victory from her first slam win, and on Thursday night, she certainly looked the part of an up-and-comer with the strokes and demeanour to go far.

Afterward, Williams dismissed the notion she was fatigued from a grueling three-set quarterfinal against Simona Halep that concluded less than 22 hours before the semifinal started (Pliskova, whose quarterfinal was earlier Wednesday, watched, then slept in until 1 p.m. on Thursday).

Instead, Williams and her coach, Patrick Mouratoglou, pointed to the left leg that she repeatedly clutched.

"When you're hampered, you're thinking of other things. Like, I was making errors that I never make, and definitely I didn't make in this tournament in particular. So many simple, simple shots that I easily could have made," Williams said. "I just blame that on just mentally thinking about my leg and just not thinking about the shot."

Kerber looks like number one 

Angelique Kerber earned the number one ranking before she stepped on court, then she went out there and looked like a top-ranked player.

Kerber is into her third major final of the year after dispatching Caroline Wozniacki in straight sets at the U.S. Open. She won the first four games en route to a 6-4, 6-3 victory that set up a rematch with Karolina Pliskova, who denied the German lefty the No. 1 ranking a few weeks ago then handed it to her Thursday night.

At the start of 2016, Kerber had never made a Grand Slam final. She could end it as a two-time major champ.

She's already the oldest woman to reach number one for the fist time at 28 and the first German since her idol and mentor, Steffi Graf.​​

On match point, Kerber hit a backhand that appeared to be heading long, and Wozniacki was going to let it go until she realized it might have clipped the baseline. She swung too late and sent the ball sailing out to end the match instead of challenging the call.

"I got a few texts, but that just made me feel worse," Wozniacki said later.

"But clearly should have" challenged it, she added. "But at the end of the day, I don't think it would have made a difference."