Two highly anticipated match-ups in Wimbledon round of 16

Today we all take a rest from Wimbledon, and tomorrow we get the entire round of 16. Included in those contests is a match between Kim Clijsters and Justine Henin. This will be the third time they have met since Henin returned to the tour. Both of their other matches this year were played on hard courts, both were decided by tiebreaks, and both were won by Clijsters. Throughout their careers, Henin has won three of their four matches on grass, including the last two, in 2006. One of those was a Wimbledon semifinal.

The Belgians have played each other a total of 24 times, and each has won twelve matches. Eleven of those matches were finals, of which Henin won seven. And four of those finals were played at majors, where Henin won them all.

Few, if any, would argue that--during their first careers, when the stakes were high--Henin had a mental edge over her countrywoman. Does she still have it, or have Clijsters close 2010 victories gotten into Henin's head? Is one of them a better grass player, and will it matter?

If the much-anticipated match between Henin and Clijsters doesn't interest you much, take heart: Another round of 16 match features Serena Williams and Maria Sharapova. They haven't played one another since Williams defeated Sharapova in the 2008 Charleston quarterfinals, and their head-to-head is a lopsided one: Williams has won five or their seven matches. Still, there is interest because one of Sharapova's wins was in the Wimbledon final of 2004. Her other win was also big: She defeated Williams in the final of the 2004 tour Championships. Williams has beaten Sharapova twice at the Australian Open, and one of those times occurred during a final.

Clearly, given their history--and given how much Sharapova has struggled in recent months because of injury, incompetent medical care, and resulting problems with her serve--top seed Williams is the favorite to win this match. A win by Sharapova, at this point, would be quite an upset.

As interesting as these two matches are sure to be, however, there are other round of 16 matches that are well worth watching:

Jelena Jankovic has never played beyond the round of 16 at Wimbledon. Her opponent this year is Vera Zvonareva, who says she is not quite in form yet, but who looked plenty in-form against 15th seed Yanina Wickmayer in the third round. The "something extra" that Jankovic has added  is hitting down-the-line winners with her forehand, as opposed to just using her famous backhand for the shot.

Agnieszka Radwanska and Li Na have played each other three times, and Radwanska has won both matches that were played on grass. She is obviously favored in this match, but both women are quietly and skillfully moving through the draw, and Li has obviously lost some of her discomfort with grass play.

Petra Kvitova played some of her best tennis against Victoria Azarenka in the third round, and she also defeated 2008 semifinalist Zheng Jie. Kvitova is a hit-or-miss player, but if she stays calm and swings with some authority against Caroline Wozniacki, she could move Wozniacki out of her comfort zone.

2007 finalist Marion Bartoli plays Tsvetana Pironkova, who is known for pulling big upsets, but who is equally known for displaying mental fragility at big moments. Klara Zakopalova plays qualifier (and former top 20 player) Kaia Kanepi. Both women are playing very good tennis at Wimbledon, and this is most likely going to be a match worth watching.

Finally, Venus Williams plays Jarmilla Groth, who may or may not handle the occasion. If she handles it, she may provide Williams with her best match so far. Groth looks comfortable on the grass. So far, in six sets, she has hit 81 winners, made 55 unforced errors, and been sucessful at the net 70% of the time. She also has an average first serve win percentage of 75. This will be the first meeting between Groth and Williams.