LONDON, England - Friday's semifinals see Serena Williams continue her quest for that elusive singles gold medal against Victoria Azarenka, while the other match is an all-Russian affair between Maria Kirilenko and Maria Sharapova.
 Victoria Azarenka (BLR #1) vs.  Serena Williams (USA #4)
Head-to-head: Williams leads 8-1
Four weeks after losing to Serena Williams in the Wimbledon semifinals, Victoria Azarenka returns to Centre Court to take on the same opponent for a place in the Olympic final. On that day, Williams produced two sets of near-flawless tennis and a repeat performance will leave Azarenka up against it once more.
Nevertheless, Azarenka will go into the encounter with spirits raised after putting in her best showing of the tournament to defeat in-form Angelique Kerber in the quarterfinals. After a few stuttering performances in the opening few rounds, against Kerber, she looked like the World No.1 again, her groundstrokes crisp and her movement sharp. More of the same will be required against Williams.
Ominously, Williams believes she is playing even better tennis now than at Wimbledon, and judging by the results, few would argue with this statement. En route to the last four the American has conceded a miserly 13 games and now stands just two wins away from capturing one of the few titles absent from her resume.
 Maria Sharapova (RUS #3) vs.  Maria Kirilenko (RUS #15)
Head-to-head: Sharapova leads 3-2
Four years ago in Beijing, Russia provided all three medalists in the singles competition. Surprisingly, the two Marias, Sharapova and Kirilenko, were not amongst those on the podium. This time around, one of them is guaranteed a medal. What remains to be seen is what color it is.
After easing herself through the first few rounds, Sharapova clicked into top gear on Thursday when she produced some of her best grass court tennis in recent years to defeat Kim Clijsters in straight sets. Against Clijsters, the Russian served well, returned even better and showed her characteristic iron-clad self belief to overcome a slight second set wobble.
Yet none of this is likely to concern Kirilenko, who made her way to the semifinals in equally impressive fashion, defeating 2011 Wimbledon champion Petra Kvitova with a textbook display of counterpunching tennis. If she can do this once more against Sharapova then she has the potential to repeat her shock win at the 2010 Australian Open. However, when confronted with Sharapova's arsenal of weapons, that is a big if.