Source: anaivanovic.com Ana Ivanovic

Ana Ivanovic, who my blog readers know is my favorite tennis player has switched rackets. The 20-year-old Serbian beauty will play the Australian Open--which begins Monday--with a Yonex racket in her hand. Ivanovic had played her entire career with Wilson rackets.

"Yonex presented us with an attractive offer, but the racket was really the most important thing," said Gavin Versi, one of Ana's representatives. "She had never tried any racket other than Wilson. She just grew up using one brand never knowing if it was the best one. But she tried Yonex and loved it."

Versi wouldn't divulge contract details, citing confidentiality, but one source told CNBC that it's a four-year deal that could hit eight figures if Ivanovic is ranked No. 1 for about half the deal. Ivanovic begins the season ranked fourth in the world.

Versi told CNBC that before Ivanovic signed the deal she spent three days at the end of the season extensively testing the Yonex rackets with an independent racket technician present. After trying three different models (38 rackets in total with different customizations) she settled on using the model Lleyton Hewitt uses--the RQiS 1 Tour.

Ivanovic, who has endorsement deals with Adidas, Juice Plus and Verona Motors, is expected to be the new face of Yonex, being that she is the brand's highest ranked player.

Now, we'll give you the CNBC Racket Sponsors Rankings. Each brand gets one point for having a man or woman in the top 10. Their ranking is in parentheses next to their name.

1. Prince, 6 points. Jelena Jankovic (3), Nikolay Davydenko (4), Maria Sharapova (5), David Ferrer (5), Daniela Hantuchova (9) and Marion Bartoli (10)

2. Wilson, 5 points. Justine Henin (1), Roger Federer (1), Novak Djokovic (3), Serena Williams (7) and Venus Williams (8)

T3. Babolat, 3 points. Rafael Nadal (2), Andy Roddick (6) and Fernando Gonzalez (7)

T3. Head, 3 points. Svetlana Kuznetzova (2), Richard Gasquet (8) and Andy Murray (9)

4. Yonex, 2 points. Ana Ivanovic (4) and David Nalbandian (10)

5. Fischer, 1 point. Anna Chakvetadze (6)

For fun, here's the CNBC Clothing Sponsor Rankings. Same scoring applies. As far as I can tell, Marion Bartoli doesn't seem to have a clothing sponsor.

T1. Nike, 5 points. Roger Federer (1), Rafael Nadal (2), Maria Sharapova (5), Serena Williams (7) and Daniela Hantuchova (9).

T1. Adidas, 5 points. Justine Henin (1), Novak Djokovic (3), Ana Ivanovic (4), Anna Chakvetadze (6) and Fernando Gonzalez (7).

3. Lacoste, 2 points. Andy Roddick (6) and Richard Gasquet (8).

T4. Fila, 1 point. Svetlana Kuznetsova (2).

T4. Reebok, 1 point. Jelena Jankovic (3).

T4. Airness, 1 point. Nikolay Davydenko (4)

T4. Lotto, 1 point. David Ferrer (5).

T4. Steve & Barry's, 1 point. Venus Williams (8).

T4. Fred Perry, 1 point. Andy Murray (9).

T4. Yonex, 1 point. David Nalbandian (10).

Questions?  Comments?