Updated: May 1, 2013, 9:07 AM ET

Tennis Power Rankings

By Jon Levey
Special to ESPN.com

The spring season kicked into full gear with the tours shifting from the hard courts of Miami to the clay of Europe, with Fed and Davis cup ties sprinkled along the way. Serena Williams went undefeated, Novak Djokovic proved his mettle and Rafael Nadal saw his Monte Carlo title streak run its course. As always, these rankings are a subjective take on who's been making an impact in the pro game over the past month. Agree? Disagree? Make your opinions (rancor) known.

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2013 Power Rankings: April
RANK	PLAYER	TRENDING	COMMENT
1	Serena Williams	5 Last Month: 6	Williams took a bicycle to work on her way to a record sixth Miami title, then moved up the coast to Charleston to win her opening clay-court event. She returned to Florida for two singles wins in the U.S. victory over Sweden in Fed Cup. Williams is 25-2 so far this season and 73-4 since April 2012. Dominance thy name is Serena.
2	Novak Djokovic	2 Last Month: 4	A tender ankle and being in Boise couldn't stop Djokovic from securing a Davis Cup win for Serbia over the United States. Djokovic then limped over to Monte Carlo and struggled in his first few matches before finding his clay feet and grinding Nadal down in straights in the final. Which finishes higher in 2013: Djokovic's ranking points or the Dow Jones?
3	Rafael Nadal	2 Last Month: 1	There were three things you can count on in life: death, taxes and Nadal winning in Monte Carlo. Rafa did, however, win his eighth Barcelona title in nine years. So stiff Uncle Sam at your own peril.
4	Maria Sharapova	1 Last Month: 3	Sharapova came one match short of pulling off the Indian Wells-Miami double. For more than a set, she looked to be the better player in the Miami finals against Serena, but 10 straight games for Williams spelled 11 straight head-to-head losses for Sharapova. On the bright side, with Sharapova's title in Stuttgart and new Porsche endorsement deal, she now has more 911's than Jerry Seinfeld.
5	Andy Murray	4 Last Month: 9	Murray started his clay-court season by getting drummed in less than an hour by Stanislas Wawrinka in Monte Carlo. This came after Murray won his "hometown" tournament in Miami in a thrilling final, which turned into the Heidi game for tennis fans.
6	Victoria Azarenka	1 Last Month: 5	Now the injured reserve portion of our rankings. Azarenka hasn't suited up since withdrawing from Indian Wells with an injured right ankle. Estimated next sighting: Madrid.
7	Roger Federer	-- Last Month: 7	Federer and his achy back have also stayed on the sideline since Indian Wells. That, however, did not stop reclusive Nobel Prize-winning author J. M. Coetzee from admitting to being a closet Federer fan, describing Federer's best tennis as "something like the human ideal made visible." And also saying watching Federer play is "very much like my response to masterworks of art." It's about time somebody showed Federer a little love.
8	Jo-Wilfried Tsonga	3 Last Month: 11	After picking up two singles wins on clay in Argentina for Davis Cup, Tsonga reached the final four of a Masters Series event for the first time on the surface in Monte Carlo. Just more ammunition for the French to be irrationally disappointed if he comes up short at Roland Garros.
9	Li Na	11 Last Month: 20	Li made a comeback to the courts with a quarterfinal showing in Miami and a finals run in Stuttgart. But perhaps the bigger accomplishment was making Time magazine's list of 100 most influential people in the world -- holding a spot in the icon category -- and gracing one of the seven special-edition covers. Her six-pack on the inside pages was also a nice juxtaposition to Chris Christie's ... gravitas?
10	David Ferrer	-- Last Month: 10	Ferrer suffered a gut-punch loss in the finals of Miami -- a third-set breaker to Murray after holding a championship point -- then flamed out in the first round of Barcelona. He'll get off the canvas, though. Opponents must see Ferrer and conjure Apollo's trainer, Duke, in "Rocky II": "I saw you beat that man like I never saw no man get beat before, and the man kept coming after you. We don't need that kind of man in our life."
11	Juan Martin del Potro	9 Last Month: 2	After a great run at Indian Wells Del Potro has hit a rough patch -- losing his first match in Miami and getting upset in the third round of Monte Carlo. The new buzz cut obviously doesn't agree with him.
12	Roberta Vinci	9 Last Month: NR	Vinci hit a career-high singles ranking of No. 12 after beating Kvitova in the final of Poland. The following week in Fed Cup against the Czechs, Vinci repeated the favor against Kvitova and clinched the tie with a win over Safarova. The Italians are the early favorites in the November final against Russia. Get ready to pop the Riunite!
13	Agnieszka Radwanska	3 Last Month: 16	Radwanska won three consecutive three-setters, and hit perhaps the shot of the year -- an impossible, no-look, behind-the-back volley winner -- on her way to the Miami semis. Surprising stat time: Of Radwanska's 12 career singles titles, only two have come on clay. She has the game of a mudder, but seems to prefer a fast track.
14	Sara Errani	6 Last Month: 8	Errani lost to Sharapova (again) in the quarters of Miami and played Wade to Vinci's LeBron in Italy's Fed Cup win over the Czechs.
15	Tommy Haas	6 Last Month: NR	Haas lost early in Houston, but anybody who beats Djokovic on a hard court deserves props. Haas was ranked No. 145 last year, now he's inside the top 15. Plus, he's 35. The last time he beat a No. 1, a gallon of gas cost $1.22 (true story). His Twitter tagline says it all: Father and still tennis player.
16	Petra Kvitova	1 Last Month: 15	Kvitova lost to Vinci in the finals of Poland and again a week later in Fed Cup -- along with a win over Errani -- when the Czechs lost to Italy. Finally, the Kvitova-Vinci rivalry we've all been clamoring for.
17	Richard Gasquet	4 Last Month: NR	Gasquet followed up his semis run in Miami with a surprising loss to Fognini in the quarters of Monte Carlo. So far in 2013, Gasquet is 7-2 in three-set matches and 4-4 after dropping the first set. No one will ever confuse him with Jimmy Connors, but Gasquet is starting to show some moxie.
18	Caroline Wozniacki	6 Last Month: 12	After suffering early than expected exits from Miami and Charleston, Wozniacki caddied for boyfriend Rory McIlroy during the Par 3 contest at the Masters, chunking a tee shot into the drink. She then got bounced in the first round at Stuttgart. All in all April was not a representative month for Wozniacki's superior hand-eye coordination.
19	Milos Raonic	1 Last Month: 18	With two singles wins against Italy, Raonic spearheaded Canada's unprecedented trip to the Davis Cup semifinals, where they will face Serbia in September. In the meantime, Raonic enters his playing-with-house-money part of the calendar, otherwise known as the clay-court season. His semis run in Barcelona was like drawing 5 on a 16.
20	Jelena Jankovic	1 Last Month: NR	Look who's back. In February, Jankovic won her first singles title (Bogota) since 2010. This past month she got to the semis of Miami and backed that up with a finals showing in Charleston, where she took a set from Serena before going bonkers over pace-of-play nonsense. Oh, how we've missed her.
Biggest Jump: 11 Biggest Drop: 9