Power rankings: Venus' resurgent AusOpen run puts her at No. 5

Welcome to SI Tennis’ Power Rankings – a new recurring feature on SI.com that goes beyond the regular ATP and WTA rankings to grade and rank the top 20 men's and women's players by more than just points earned on tour. While tournament results and quality of play are considered, SI Tennis’ Power Rankings also take into account those unquantifiable metrics that make the sport so compelling—everything from injuries and meltdowns to big upsets and recent title wins, as well as other subjective assessments. Each edition of SI Tennis Power Rankings is intended to capture a more seasonal and timely portrait of the current tennis rankings.

Check out our first edition here, the newest ATP Power Rankings here and the newest WTA Power Rankings below.

1. Serena Williams

Previous Power Ranking: 1

With No. 19 in the bag, Serena's quest, now begins in earnest, to catch Steffi Graf's mark of 22 majors. In the end she reminded us why, at her best, she is the best: That serve. It's going to take a lot to beat a woman who can fire 18 aces in a two set match. 

2. Maria Sharapova

Previous Power Ranking: 2

She said it herself: There's no disgrace in losing to Serena. She's started the season with a 10-1 record and solidified her No. 2 ranking in Melbourne.

3. Simona Halep

Previous Power Ranking: 3

For the second straight year, she flopped in the quarterfinals of the Australian Open, putting in a shockingly poor performance. She does have a title this season, though. 

4. Petra Kvitova

Previous Power Ranking: 5

Hit off the court by Madison Keys in the third round, the loss doesn't look so bad in retrospect. Her improved fitness was notable and should serve her well as the season progresses. And she still left Australia with a title, having won the Sydney International the week before the Australian Open.

5. Venus Williams

Previous Power Ranking: 7

Venus could have easily found herself in the semifinals, having led Keys by a break in the third set in the quarterfinals. But on the whole, she couldn't have asked for a better start to the season. She beat Caroline Wozniacki to win Auckland and followed it up with a good win over Agnieszka Radwanska in the fourth round of the Australian Open.

6. Agnieszka Radwanska

Previous Power Ranking: 6

One thing about hiring a legend as a coach: the scrutiny is unavoidable. She played a passive match against Venus in the fourth round, but has looked good otherwise.

7. ANA IVANOVIC 

Previous Power Ranking: 4

It's just something about the Slams. Ivanovic continued her struggles on the big stage, losing in the first round to Lucie Hradecka. But she'll remain a force in the tour events.

8. Caroline Wozniacki

Previous Power Ranking: 9

When the season ended in October, Wozniacki was on many short lists as a favorite to win the Australian Open. Instead, she was completely outplayed by Victoria Azarenka in their blockbuster second round match. Plus there are possible wrist injury concerns. Wozniacki has to reassert herself over the next two months before the tour turns to her worst surface, clay. 

9. Ekaterina Makarova

Previous Power Ranking: 12

She quietly blitzed her way into her second consecutive Slam semifinal, beating the hot hand, Karolina Pliskova, as well as Halep. But can she make an impact at the tour-level events?

10. Madison Keys

Previous Power Ranking: Out of Top 20

An incredible breakout run saw her beat Kvitova and Venus to make her first Slam semifinal, all the while unveiling one of the most powerful games on the women's tour. But the question for Keys has always been consistency. The next few months will be a big test of that. 

11. Eugenie Bouchard

WTA Ranking: 7
Previous Power Ranking: 10 

She looked great through Melbourne until she played a poor match against Sharapova in the quarterfinals. At what point will Bouchard realize she's too good of an athlete to simply rely on first-strike tennis? When her aggressive game isn't there she chooses to just keep hitting as opposed to using her legs to get back into the match. Hopefully a new coach will change that. 

12. Karolina Pliskova

Previous Power Ranking: 11

Given her strong momentum coming into Melbourne, the third round loss to Makarova was disappointing. But she remains one to watch on the hard courts.

13. ANgelique Kerber

Previous Power Ranking: 8

What an odd January for Kerber. Her three losses came to players ranked No. 28 (Svitolina), No. 22 (Pliskova), and No. 42 (Begu). 

14. Victoria Azarenka 

Previous Power Ranking: Out of Top 20 

Her form in Melbourne was very encouraging. The win over Wozniacki was her best level in over a year and her tight loss to Cibulkova in the fourth round deprived us of what would have been a great quarterfinal match-up with Serena. So long as she stays injury free, Azarenka will be back near the Top 10 sooner than you think. 

15. Garbine Muguruza

Previous Power Ranking: 15

Once again, the Spaniard showed she knows how to play Serena. She took a set off the American in the fourth round, her best result ever in Melbourne. 

16. Dominika Cibulkova

Previous Power Ranking: Out of Top 20

I'll be frank, I didn't give Cibulkova a shot of making the second week in Melbourne. She didn't defend her final points from 2014 but she played some of her best tennis to beat Flipkens, Pironkova, Cornet and Azarenka before losing to Serena. If she can hold that level, she'll stay in the Top 20.

17. Alize Cornet

Previous Power Ranking: 13

Her straight set loss to Cibulkova was surprising, but she's still a dangerous force on the tour.

18. ELINA SVITOLINA

Previous Power Ranking: 19

She took a set off Serena in the third round and, on the whole, had a very good start to the season. All three of her losses came to Top 10 players (Sharapova, Makarova and Serena.) 

19. BARBORa ZAHLAVOVA STRYCOVA​

Previous Power Ranking: 20

She lost in straight sets to Azarenka in the third round but it was a good trip Down Under for the Czech, as evidenced by her No. 12 ranking in the Road to Singpore rankings. 

20. Madison Brengle

Previous Power Ranking: Out of Top 20

It's hard to ignore the January Brengle had. She made her first WTA final in Hobart and then made her best run ever at a major, making the fourth round. She went 14-3 in January, with her one Top 20 win coming over Andrea Petkovic in Melbourne. Still, wins build confidence, and Brengle was incredibly consistent.