Federer vs. Del Potro:  Much like Tsonga late in 2011, the Argentine would have compiled a spectacular record this year if he only could have discovered a solution to Federer.  Five times since January has the Swiss dismissed the man who conquered him at the US Open three years ago, perhaps still harboring an appetite for revenge.  Whether or not their rivalry has acquired a personal dimension from Federer’s perspective, he has displayed some of his finest tennis in blunting Del Potro’s power and exposing his flaws, most notably his forward movement and his ability to reverse direction along the baseline.  At Roland Garros, the Argentine advanced towards the brink of turning the tables, crushing groundstrokes past the Swiss as he built a two-set lead.  Continuing a concerning trend in his career since surgery, however, Del Potro abruptly collapsed while winning just five games over the next three sets.  Such setbacks against the ATP elite have grown predictable for him since 2010, for he repeatedly has won sets or forced tiebreaks in such encounters only to suffer a failure of nerve when the match hangs in the balance. 


Having deadened Isner’s serve with stylish grace, Federer has reached the medal rounds at the Olympics for the first time in twelve years.  Although Del Potro’s first-strike power should produce plenty of entertainingly explosive exchanges, the reigning Wimbledon champion has moved better on this surface than anywhere else in 2012 and will know how to make it reward his versatility.  The Argentine has proven before that he can defeat Federer when it matters most, but he will not compete for a gold medal unless he rediscovers the willpower without which his serve-forehand combinations count for little on such grand occasions.


Murray vs. Djokovic:  Until this summer, the recently dethroned #1 never had met two of his three main rivals on grass.  His initial confrontation with Federer there last month did not proceed according to his plans, so he will hope for greater success against the Wimbledon runner-up.  At the most significant tournaments where they have clashed, the Australian Open and the two miniature majors at Indian Wells and Miami, Djokovic has dominated Murray with five victories in six meetings.  Especially prolific during the North American summer, the Scot swept all three of their clashes during the US Open Series as the Serb’s form sometimes has declined from the first half to the second half.  If he aims to cast aside the reputation of a talented player who wins the unimportant matches in rivalries and loses the important encounters, Murray could take an immense step forward here by clinching at least a silver medal.  Relegated to the bronze medal in Beijing, Djokovic committed fateful errors late in an edgy semifinal there.  A similarly tense mood could shroud this Olympic semifinal, which pits a man burdened by the expectations of his nation and a series of highly visible heartbreaks against a man who may desire a medal so much that he could cripple himself with self-inflicted pressure. 


Despite their elevated rankings, Djokovic and Murray rarely have performed at a high level simultaneously but instead often have collaborated on either uninspired or downright dismal tennis.  Lethal and limp in alternating matches so far this week, the Serb must produce a more sustained effort from start to finish, while the home hope must shield his paltry second serve from his rival’s return.  Both seek to thrust Wimbledon disappointments behind them, and the winner likely will earn a rematch with the architect of his demise.


Azarenka vs. Serena:  Through four matches, the Wimbledon champion’s opponents have collected one more game than she has won in each match while eating two bagels and two breadsticks.  Whereas Serena’s serve extricated her from many a predicament at the All England Club a month ago, every weapon in her fearsome arsenal has fired consistently in a stunning pyrotechnic display this week.  Rare is the tournament where this champion surges to the title without a single difficult match or lull in form, however, and her semifinal opponent seems the most probable of the three women remaining in the draw to pose that obstacle.  Although she has secured only one victory over Serena in her career, Azarenka possesses the balanced baseline game and the combative mentality to stand toe to toe with the living legend.  Her single glaring weakness, an unimposing first serve, has proved her undoing again and again during her four losses to Serena over the last twelve months.  But she has competed vigorously in three of those four matches, including two encounters at majors that followed a similar pattern.  After Serena established her supremacy with a commanding first set, Vika fought back into contention with an intelligent, crisply focused second set that escalated to a tiebreak before her rival narrowly avoided a final stanza. 


A solid victory over Kerber behind her, Azarenka also defeated potentially dangerous dark horses Martinez Sanchez and Petrova on a surface where she normally has shone less than on hard courts.  As she typically does against Serena, she will aim to extend the rallies and measure her groundstrokes closely to the baseline, forcing the American to create her own angles and testing her footwork.  On grass, Azarenka will struggle more than anywhere else to overcome the differential in first-strike power, but this semifinal should thrill if she can start the match as she finished their Wimbledon semifinal—and maintain that quality throughout.  The best player in the WTA through the first few months of 2012, she now hopes to wrest away the ascendancy from the best player in the WTA this summer. 


Sharapova vs. Kirilenko:  When champions collided on the eve of the medal matches, the Russian flagbearer rose to the occasion for her finest performance of the week.  Dismantling her fellow four-time major champion in straight sets, Sharapova devastated Clijsters with vicious returning on both first and second serves, a pattern that should continue against her compatriot.  For her part, Kirilenko deserves high praise for solving 2011 Wimbledon champion Kvitova in a match during which she clung doggedly to her serve while subjecting her opponent to relentless pressure.  The unlikely medal contender exploited her forecourt talents with sharply angled volleys and deft touch that left her far more powerful opponent frozen on key points.  Comfortable in every region of the court, Kirilenko committed just a single unforced error in a display of stinginess that she will need to repeat while Sharapova attempts to replicate her aggressiveness in return games.  None can doubt who will dictate the exchanges, for the more decorated Russian has unleashed nearly three times as many winners in her last two matches as rivals—Lisicki and Clijsters—who do not lack options to end points on their own terms.


Curiously, Kirilenko has won the first set in each of their last four encounters, of which Sharapova has rallied to win two, lost another in a third set, and retired early in the second set of the fourth.  Of equal curiosity is the fact that the less famous Russian won the most significant of their five meetings, in the first round of the 2010 Australian Open.  Never having reached a major semifinal, Kirilenko must view this match as the most important of her career to date.  But Sharapova has coveted a medal for years, so the opportunity to clinch at least silver at the expense of a former nemesis must look golden to her indeed.  A nation that embraces each of its Olympics heroes and heroines with pride, Russia will add at least one medal to the three that it earned in this event four years ago.