Li Na Li Na of China reacts after winning a point against Alisa Kleybanova of Russia during day five of the 2010 China Open at the National Tennis Centre on October 5, 2010 in Beijing, China.

Wozniacki vs. Li:  Converging for the second straight Australian Open, these baseline gladiators collaborated upon an especially ghastly fourth-round encounter here last year.  While Wozniacki uncorked just three winners, Li repeatedly shanked swinging volleys and struggled to place her first serve throughout a match that featured more breaks than holds.  Dragging each other into final sets in their two prior meetings, they mirror each other in areas such as their stinging two-handed backhands and unremarkable but reliable serves, which will lead to elongated rallies that showcase their exceptional movement and court sense.  Whereas Wozniacki favors consistency over aggression on a forehand heavy with topspin, though, Li often flattens out her forehand to target lines and corners more ambitiously.  Stretching opponents off the court laterally with acutely angled groundstrokes, last year’s semifinalist must counter the Dane’s tactic of pushing opponents behind the baseline with deep but vertically oriented gambits.

Curiously, the 20-year-old already has compiled far greater experience at the sport’s highest level than the veteran who opposes her.  With one Slam final already to her credit, Wozniacki displayed the self-belief born of that experience in her quarterfinal comeback against Schiavone.  Down a set and a break, the world #1 did not despair during a deuce service game that almost certainly would have sealed her fate had she not secured it.  With a tenacity that resembled champions of the past, she found a way to navigate through those murky waters and soon found herself rewarded as fatigue nibbled away at Schiavone.  In a contrasting manner, Li Na also has resembled past champions through her utter dominance over her first five victims, none of whom could pry more than six games from the relentless Chinese star.  Never a paragon of consistency, she has wobbled for no more than one or two games at a time throughout the fortnight.  Li regrouped immediately when early adversity struck in her victories over Azarenka and Petkovic, demonstrating an appetite for battle that she shares with her adversary.  We expect a tense war of attrition that will jangle the nerves of Piotr and Jiang before the steelier competitor captures a hard-earned berth in the final.

Vera Zvonareva Kim Clijsters (L) of Belguim and Vera Zvonareva of Russia pose before their women's singles final on day thirteen of the 2010 U.S. Open at the USTA Billie Jean King National Tennis Center on September 11, 2010 in the Flushing neighborhood of the Queens borough of New York City.

Clijsters vs. Zvonareva:  A script all too familiar to casual fans, this burgeoning rivalry between two of the top three players in the world reaches its third consecutive major.  Despite their equally lofty rankings, they have produced tepid tennis in most of their recent encounters, even excluding the unsightly US Open final.   The Russian has scored more substantial successes against Clijsters than anyone else during the Belgian’s comeback, however, and the medium-speed courts in Melbourne may tilt in her direction more than the slick surface in New York.  Increasingly accustomed to reaching the latter stages of majors, Zvonareva will have grown in self-belief with each resounding result, while the relatively relaxed atmosphere in Australia will soothe her easily awakened anxieties.  With no fatal flaws yet no striking strengths, she can ambush heralded foes like Clijsters only by maintaining focus, patience, and emotional resilience, all of which she lacked until less than a year ago.  Those traits played a central role in her three 2010 victories over the Belgian, who staggered through both third sets that they contested while Zvonareva stayed unspectacular but solid.

Even if the world #2 does curb her nerves, not an easy task in a Slam semifinal, she probably will need assistance from an opponent who can do everything that she does with just a trifle more polish and precision.  While the Russian has looked more composed and authoritative with each match, Clijsters looked invincible when she routed Safina in the first round but has grown distinctly more human with each round since then.  Over her last three matches, in fact, the Belgian has donated more than 100 unforced errors to opponents who still could not capitalize upon that generosity to steal a set from her.  Subject to more mental lapses than most champions, Clijsters continues to experience moments of negativity or doubt that can cloud her normally acute sensibilities and lure her away from the lucid point construction that has won her three major titles.  On a brighter note, she has won all three of the tiebreaks that she has contested here with minimal ado, whereas Zvonareva has struggled at times near the end of sets and matches.  Rather than the electric shot-making of the Williams sisters, Henin, and Sharapova, Clijsters and Zvonareva excel at absorbing pace and redirecting the ball.  Since their physical skills parallel each other so closely, as in the first semifinal, the psychological dimension probably will decide this encounter.  We expect many more unforced errors than winners as the exhaustive court coverage of both players coaxes their opponent into low-percentage shot selection.

Roger Federer and Novak Djokovic - U.S. Open-Day 13

Djokovic vs. Federer:  Without Nadal awaiting the winner on Sunday night, this encounter becomes even more momentous than a typical Slam semifinal although not quite a de facto final.  Having split their previous four semifinals at hard-court majors, Federer and Djokovic both seek to build upon the confidence that they gained late in 2010, when the Serb’s Davis Cup heroics swiftly followed the Swiss legend’s march through the year-end championships.  Their US Open meeting reinvigorated not only Djokovic but this fiery rivalry, rife with savagely slashed forehands, improbable defensive retrievals, and epic rallies that sprawl both vertically and laterally across the court.  Among the key advantages that the third seed long has enjoyed over the second seed is the finest two-handed backhand in the ATP, which has hammered away at Federer’s vulnerable one-hander during the Serb’s victories over the Swiss.  Yet the defending champion has enhanced that lesser wing during the last several months, flicking cross-court winners at pivotal junctures during his victory over Nadal in London.  From our perspective, though, two-handers inherently possess greater penetrative capacity than their more elegant one-handed counterparts, so Federer cannot completely erase that power gap.

Snapping his streak of three straight US Open losses to the GOAT, Djokovic looked dazed with disbelief at his accomplishment despite having pounded his chest and pumped his fist with intimidating physicality throughout the final set.  Unable to summon the same fearlessness during his three fall clashes with Federer, the Serb lost six of the seven sets that they played in Shanghai, Basel, and London amidst shrugs and self-deprecating smirks.  The post-US Open malaise may have sprung in part from Djokovic’s focus upon the Davis Cup title as the fall events ebbed towards the anticlimactic conclusion in London.  Rather than basking in the glow of his December glory, the third seed has surged through the draw of the major that he won three years ago while conceding only a single set.  Comprehensively dominant against Berdych in the quarterfinals, Djokovic suggested that he may have recaptured the swagger that brought him to the US Open final as well as the Melbourne title three years ago.  A straight-sets victim of the Serb on that occasion, Federer looked chronically fallible in the first week before recording stunning service statistics a round ago against Wawrinka.  The defending champion will face heightened pressure from his opponent’s formidable second-serve return, however, which underscores the significance of his first-serve percentage.  And the suspenseful fifth set in their US Open semifinal might never have arrived had Federer not sagged in intensity for prolonged periods throughout the first four sets.  A far more experienced and somewhat more confident competitor than the Serb, he can avenge that defeat and reclaim the psychological edge in their rivalry only if he proves that he can maintain not just form but focus across a best-of-five encounter—an increasingly complicated challenge as the years drift past.