Roddick vs. Djokovic:  Having won titles at his last two non-majors, the three-time Wimbledon finalist has displayed his most convincing tennis since reaching a US Open quarterfinal last year.  Unable to survive the first week at the first three majors of 2012, Roddick could redeem himself by shining at an event that he did not enter four years ago.  Long a reliable contributor to the American Davis Cup team, for which he accumulated a perfect record in tie-clinching rubbers, the former US Open champion always seems to gain an extra ounce of motivation when national honor lies at stake.  One could say much the same about the recently deposed world #1, the centerpiece of Serbia’s historic charge to the Davis Cup title in 2010 and one of the most recognizable individuals in his nation.  Nearly reaching the gold-medal match in Beijing, Djokovic needed to rally from a one-set deficit against Fognini to survive his first match at Wimbledon Part II.  His rivalry with Roddick, which he trails 5-3, has mirrored the peaks and valleys of his career:  a strong beginning during his initial breakthrough in 2007-08, four straight losses during his underachieving spell in 2009-10, and then a routine victory in this city at the 2010 year-end championships, a few months after he revitalized his fortunes by reaching the US Open final.  In a best-of-three format on grass, Roddick can harbor loftier aspirations than in almost any other setting, for a streak of torrid serving could carry him to victory almost by itself.   Not fond of each other in earlier years, these two major champions and former #1s could produce the most electric energy of any pairing on Tuesday.

Tsonga vs. Raonic:  Probably the most fearsome server among the ATP’s rising stars, Raonic has enjoyed scant success at the tournament most favorable to the serve.  Forced to withdraw from Wimbledon with an injury last year, he fell in the second round to the similarly towering Querrey this year.  As another battle with a fellow seismic server looms, the Canadian will need to elevate his focus for the few opportunities that emerge more effectively than he did a month ago.  Even if he misses his first serve, Tsonga will attempt ambitious second serves behind which he can hurtle to the net for a Sampras-like smash or one of his implausibly delicate volleys.  Unlike the Frenchman, Raonic prefers to finish points with his forehand from just inside the baseline, approaching the net only when a comfortable volley beckons.  A competitor defined by momentum and confidence, Tsonga will bring plenty of both qualities to a setting where he has reached the semifinal in his last two appearances.  But a turbulent three-setter against Bellucci—not exactly a grass specialist—raises fears that a breakdown may follow a breakthrough as it often has throughout the fifth seed’s career.

Lopez vs. Monaco:  Edging into the draw in the wake of Nadal’s withdrawal, Lopez has grasped his chance with both hands by winning his opener, much as Petzschner did when he replaced Karlovic.  Enjoying his best results of any major at Wimbledon, the veteran lefty recalls the era when the top left-handed men slid their serves out wide to open the court and then slipped into the net for a stinging volley before the opponent could regroup.  Notoriously unreliable on his backhand wing, however, Lopez becomes vulnerable when his opponent pins him in that corner or behind the baseline.  Suited to that objective is recent Hamburg titlist Monaco, who ventured away from grass to a clay interlude this summer that lifted him into the top 10.  Since his Miami semifinal, the Argentine has marched upwards steadily but still doesn’t seem a threat on the level of his compatriot Del Potro.  A lesser version of Ferrer, he excels at grinding down more powerful foes until either their stamina or their patience crumbles.  This match thus somewhat resembles the meeting between Roddick and Ferrer at Wimbledon last month, which produced a mildly surprising result considering the surface.

Azarenka vs. Martinez Sanchez:  Falling to the crafty Spaniard two years ago at Indian Wells, Azarenka avenged that setback twice as she has matured.  Nevertheless, she continues to struggle chronically with  left-handers, frustrated by Kvitova and even Makarova.  After striking an alarming 14 double faults in her opening victory, the world #1 joined a lengthening list of medal contenders whose hopes have grown murkier in the wake of such early frailty.  Martinez Sanchez has won few main-draw matches in singles this year, and she lost her first match at Wimbledon when she could not find her first serve with regularity.  If she can find it at key moments this time, the grass suits this natural net-rusher’s tactics and can reward her deft touch.  To gain the time to launch her creative gambits, though, she will need another fallible performance from Azarenka not only in service games but in return games.

Venus vs. Wozniak:  When they met in a Miami thriller, the Canadian improbably served for the match in the third set after breaking Venus no fewer than seven times.  Able to extricate herself from that predicament and claim the decisive tiebreak, the aging American likely leaned upon her sturdy crowd support as much as her less sturdy groundstrokes.  While she might not enjoy that advantage here, Venus started her quest for yet another Olympic medal far more impressively than her Wimbledon campaign began, dispatching world #9 Errani without suffering any serious lulls in form.  Much further into her comeback, she probably has learned how to distribute her energy throughout a match and reserve much of it for when she needs it most.  Another doubles medal with her sister surely awaits (probably gold), but Venus will not want to leave her favorite court as quietly as she did last month.  

Lisicki vs. Shvedova:  Both having reached a major quarterfinal this summer, both bring more momentum into the Olympics than some of their higher-ranked opponents.  Although her own ranking has sagged slightly, Lisicki reasserted herself after a long absence from contention by upsetting the top-seeded Sharapova at Wimbledon.  Of a similar magnitude was Shvedova’s victory over defending champion Li at Roland Garros, which preceded tight three-set losses to Kvitova there and Serena on grass.  The German has cultivated a habit of turning routine matches into uncomfortable affairs, as her narrow escape from an ITF wildcard in the first round illustrated.  For her part, Shvedova continues to waver occasionally when trying to deliver the terminal blow late in matches, sometimes seizing defeat from the jaws of victory.  This dynamic should produce an entertaining, unpredictable meeting between two women who club virtually every ball without mercy or subtlety.  In a match where rallies will end quickly, neither woman can afford to stay on the defensive for long.

Sharapova vs. Robson:  In their only previous meeting, the plucky British teenager temporarily alarmed the 2004 Wimbledon champion on Court 1 last year.  Establishing an early lead with smart point construction and well-placed serves, Robson thrilled her home fans until Sharapova found her range from the baseline.  When the first-set tiebreak arrived, the Russian’s experience allowed her to seize the initiative for good while her challenger faded.  Savoring her Olympics debut so far, Sharapova crushed Peer under the roof with intensity more sustained than she showed during her unimpressive Wimbledon campaign.  Meanwhile, Robson sparkled in a dangerous match against fellow hard-hitting lefty Lucie Safarova, so she should bring ample confidence to Centre Court as well.  From Oudin to Garcia to Watson to Robson herself, teenagers have troubled Sharapova at majors on her mortal days.  Despite the sharp contrast in their accomplishments to date, then, the British prodigy should not yield too meekly.