Among the matches scheduled for Saturday lurks a possible preview of a clash that could recur with a medal at stake in a few weeks.  We speak not of any singles encounter but of the doubles match that pits Kirilenko and Petrova against the Williams sisters.  The defending gold medalists from 2008, Serena and Venus might encounter some of their sternest competition in 2012 from the two Russians, who won Miami together before finishing runner-up to Errani and Vinci at both Roland Garros and the Dutch Open.  (Remarkably, Kirilenko and Petrova also fell to the Italian team in a Madrid semifinal and a Rome quarterfinal.  And whom did they defeat for the Miami title?)  While Venus can afford to focus on that marquee doubles collision, Serena must resolve a bit of business earlier in the afternoon.  We start there on Saturday.

Serena vs. Zheng:  In the last Olympic year, Wimbledon showcased a semifinal between the legendary champion and the tenacious battler from China.  Once she adjusted to the pace of Serena’s serve on grass, and once Serena relaxed a little, Zheng improbably stretched her far more decorated opponent into a second-set tiebreak.  Rarely does her focus ebb, an advantage that she holds over elite women of greater power.  Serena could testify to that underestimated strength of the diminutive doubles specialist, having watched a 5-0 lead slip away in a set that they contested in Miami, during a match that became a scintillating three-setter.  Defeating Sharapova at Indian Wells two years ago, Zheng knows how to redirect pace and pin heavy hitters behind the baseline with her deep groundstrokes. Yet her short wingspan leaves her vulnerable to Serena’s wide serves, a weapon that should earn the four-time champion plenty of free points.  And she will want to maximize her first-serve percentage, for her shallow second serve usually offers a target for returners as explosive as the American.  Although Serena has not delivered the overwhelming displays of power here that she unleashed in Madrid, especially on return, her steadiness and relative calm suggest that she has suffered no loss of confidence following her first-round loss in Paris. 

Ferrer vs. Roddick:  Arguably his most impressive win at a major since the Wimbledon semifinal three years ago, a four-set triumph over the Spaniard at the US Open propelled Roddick into a quarterfinal last fall.  Not a man to let disappointment deter him, Ferrer wasted little time in earning his revenge at the Shanghai tournament a month later, remarkably conceding no breaks of serve through three sets.  Likely buoyed by his Roland Garros semifinal appearance, the dirt devil has reached the penultimate round at every major but the All England Club.  Grass does not offer an accommodating stage for the talents of counterpunchers and consistency experts, nor does it welcome those who attempt to hit forehands from the backhand side of the court, as does Ferrer.  On the other hand, the surface adds ever more acceleration to Roddick’s serve, the shot that carried him to three finals on this court—and three losses to Federer.  Not quite as impenetrable on serve as in his prime, even here, the American navigated through plenty of arduous holds against the unheralded Jamie Baker.  Demonstrated in his victory over Roddick on a fast indoor court in Davis Cup last summer, Ferrer excels in making contact and at least punching the ball back into play.  Much may hinge on the three-time finalist’s success in the forecourt, an area that his serve should allow him to reach but where his opponent’s passing shots will punish him for an approach less than excellent.  As he has against Nadal, Roddick might turn back the clock to rely on serve-volley tactics more frequently, including with his second serve. 

Nishikori vs. Del Potro:  A quarterfinalist at the Australian Open, Nishikori has struggled with injury too often to establish himself as a consistent contender so far.  His clean, compact ground strokes should adapt well to the grass, however, as should his crisp footwork.  Across the net stands a playing style more typically associated with success on grass, a towering figure with an imposing serve and balanced groundstrokes.  But, outside his serve, Del Potro lacks many of a grass player’s key attributes:  the skill in the forecourt, the inclination to go there, and the efficiency of movement.  Hovering above the grass on precarious limbs, the US Open champion prefers to take time away from his opponents rather than have the surface take time away from him.  As the tournament progresses, though, the grass appears to grow slower, so he may become more comfortable with each round that he survives.  Disappointingly tepid in several of his losses this year, Del Potro still has not lost to an opponent outside the top 10 since the Australian Open, a streak that he should extend in a battle played largely from his baseline comfort zone.  Somewhat like Ferrer in his fondness for wars of attrition, Nishikori should assist Del Potro in settling into rhythmic rallies, where the superior weight of the Argentine’s shots should prevail. 

Ivanovic vs. Goerges:  More comfortable on clay than grass, the brunette relies on heavy serve-forehand combinations with more spin than the surface usually rewards.  That sentence could describe either of the lovely ladies on display in the most glamorous women’s match of the weekend.  Although she reached the second week of the Australian Open, the German’s greatest accomplishment likely remains the clay title in Stuttgart last year that catalyzed a strong spring campaign.  Doomed by fading light at Roland Garros this year, the crepuscularly challenged Goerges showed scant intent to redeem herself on grass when she entered Bad Gastein on clay as the top seed a week later—and lost her first match.  Less surprising than her two victories, therefore, is the occasionally unconvincing form that she has shown here.  Again, one could say the same about Ivanovic, who entered Wimbledon bereft of grass preparatory matches and must count herself fortunate to avoid consecutive three-setters.  Better than the sometimes wooden Goerges at handling low balls, she deploys less elongated swings on her groundstrokes.  Those advantages aided Ana in recording a routine victory over the German in their only previous meeting on grass.  As she scrapes off the rest of her rust, whiplash could lie ahead in a match between two women who oscillate wildly and unpredictably in their execution.

Cilic vs. Querrey:  Littered with towers of power is this section that once contained Karlovic, Raonic, and Kevin Anderson in addition to Roddick and these two leviathans.  As a result, serving clinics have set the tone in a return to the days when points at Wimbledon seldom lasted more than two or three shots.  Overcoming arguably the tournament’s most dangerous dark horse in Raonic, Querrey responded with surprising poise to various forms of adversity.  Down triple break point in his third service game of the match after failing to break Raonic in the previous game, he doused the flames of that threat rather than succumbing to disappointment.  Failing to serve out the second set, something that a server of his quality never should fail to do against a returner of Raonic’s quality, he nevertheless regrouped to win a second-set tiebreak that he absolutely needed to have.  When darkness fell on the All England Club, he did not lose his focus in a delicately poised affair but returned the next day to win the 18-point tiebreak that effectively proved decisive.  Riding an eight-match winning streak, meanwhile, Cilic hopes to continue his momentum from the Queens Club title.  Armed with a formidable backhand, he will win the vast majority of exchanges between their two-handers and should aim to exploit his superior groundstroke symmetry whenever he maneuvers himself into a rally on Querrey’s serve. 

Goffin vs. Fish:  After an alarming sequence of events following the Miami tournament, where he reached the quarterfinals, the world #12 finally returned to the sport this week with a pair of heartening victories.  Despite reporting indifferent health after his first match, Fish marched through a five-setter in a surprising display of stamina; before his recent absence, in fact, he often had struggled mentally when matches reached that stage.  No longer the top-ranked American, he looks far more natural and at ease with himself than he did when he held that position and shouldered the expectations that came with it.  Far from ordinary in terms of his talents, Fish has remained a thoroughly ordinary, unassuming figure and shines the most when he receives the least attention.  A quarterfinalist at Wimbledon before, he has won a set from Nadal on these lawns behind a vintage net-rushing style.  As long as his first serve fires regularly, he should conquer the less intimidating game of Goffin.  Sometimes compared to Davydenko, the Belgian deserves great credit for winning two matches in the major after his second-week breakthrough at Roland Garros, when few would have faulted him for suffering a hangover.  While players usually make their own success, sometimes success plays a role in making the player, who in this case has more than justified his wildcard.  Suddenly a brave competitor, Goffin did not let Tomic cow him in a second-round comeback, so Fish faces a fierce foe fit for a fight.