US Open Tennis 2013: Previewing Friday's Women's Semifinals

Finally, we're going to see a woman make her second Grand Slam final of the year.

2013 has been an unpredictable, parity-filled year on the ladies' side, with six different individuals making up the first three major finals of the season. 

But with three of those six still alive in New York as we near the semifinals, we are assured that at least one will break the trend of 2013. 

Let's take a look. 

Note: You can find Day 12's full Schedule of Play here and the updated draws here, courtesy of USOpen.org

Flavia Pennetta vs. (2) Victoria Azarenka

At first glance, this seems like a lopsided battle. Victoria Azarenka is coming off an impressive tournament win in Cincinnati in which she beat the unbeatable Serena Williams, she has a major victory on a hard court and she made it to the final last year at New York.

Pennetta, meanwhile, is ranked No. 83 in the world and has never made a Grand Slam final despite playing majors regularly for 11 years. 

But don't be so quick to write off the 31-year-old Italian. 

First of all, she thrives in New York, notching four U.S. Open quarterfinal appearances in the last six years.

Second, she is absolutely en fuego. She has defeated four-straight ranked opponents—including No. 4 Sara Errani and No. 10 Roberta Vinci—in straight sets, and it's clear she is playing the best tennis of her life right now. 

The same cannot quite be said for Azarenka. 

Although she looked more herself in the quarters, the 24-year-old Belarusian struggled to three-set wins in her third- and fourth-round matchups and has looked a little inconsistent at times. 

Granted, that up-and-down play includes some high moments, and when she's at her best, she has the return game to seriously frustrate Pennetta, who has won 75 percent of her first serves. 

In a rematch of what was supposed to be a second-round Wimbledon match in July before Azarenka withdrew, this should be a tight battle. 

(1) Serena Williams vs. (5) Li Na

If Li Na is going to have any chance of beating Williams, she's going to have to hold her serve. 

With Williams boasting, you know, arguably the greatest serve ever in women's tennis, break opportunities are going to be few and far between.

Li did manage five breaks against Williams when the two played in Cincinnati last month. But with the world No. 1 playing out of her mind right now—she has dropped just 13 games in five matches (1.3 per set!), won 81 percent of her first serves and smashed 21 aces—Li likely won't approach that number again.

If the world No. 6 wants to keep things close, she will have to serve well.

Against Williams in Cincinnati, however, she won an atrocious 46 percent of her service points and hit eight double faults, per MatchStat.com.

She has been better at the U.S. Open, winning well over 70 percent of her first-serve points while notching a tournament high 29 aces.

With that being said, holding her serve is just Step 1, as it's going to take a minor miracle to upend the favorite. She has beaten Williams just twice in 10 career matches, and when the defending champ plays how she has the last week, there is no one in the sport capable of approaching her.

Li has played well in New York, but Williams is simply too good.