As the US Open nears its midpoint, seeds begin to collide and matches become more evenly balanced. 

Jankovic vs. Radwanska:  In each of their three meetings, the Serb has won at least one set against her fellow counterpuncher.  Like her encounters with Wozniacki, the trajectory of her matches against Radwanska have traced her decline with age in execution and fitness, the latter of which emerged from third-set bagels in both of Jankovic’s losses to the Pole.  Impressive in the first two rounds, the 2008 US Open finalist may have gained momentum from reaching the final in Dallas, a crucial week for a woman who had lost eight of her previous nine matches.  Jankovic now seeks her second straight appearance in the second week at a hard-court major, which would bolster her plummeting ranking.  From Radwanska’s first two matches, meanwhile, have emerged two different visions of the world #2’s viability as a title contender.  After a commanding victory to open the tournament, she narrowly survived the pesky Carla Suarez Navarro in a war of attrition.  Since neither woman can hit the ball past the other comfortably from the baseline, expect a match of long, grinding rallies decided by unforced errors rather than winners.

Makarova vs. Serena:  Stunned by the fiery lefty at the Australian Open, Serena surely would relish the prospect of revenge on a challenger whom she must feel unworthy of her.  In Melbourne, though, she secured just five games on an afternoon when both her serve and her return abandoned her.  A surprise quarterfinalist who spurred intense enthusiasm at the time, Makarova has remained a sporadic sniper rather than become a regular contender, whether because of her moodiness or a combination of high-risk tactics and less than impeccable technique.  Lightning did strike Venus twice at majors this year in the person of Kerber, but this Russian lefty has accomplished much less than that top-10 threat.  Although Serena looked oddly lethargic for much of her second-round victory over Martinez Sanchez, regressing from an auspicious opener, the heightened quality of the competition and her recent memories of a stinging defeat should kindle her competitive spirit more than in most first-week clashes.

Ivanovic vs. Stephens:  A year ago, they met in the third round of the US Open, also during a Saturday night session on Arthur Ashe.  Clearly albeit not overwhelmingly superior then, Ivanovic won two relatively routine sets after plenty of crackling rallies.  Since she last saw the Serb, Stephens has improved significantly in both the physical and mental departments of the game.  Her first-round victory over Schiavone showcased the former area in her ability to play closer to the lines than before without sacrificing too much consistency, and her second-round triumph showcased the latter area in her brave determination to survive amidst mounting adversity.  Crucial to her eventual comeback was a ten-deuce game midway through the second set, during which she shrugged a series of horrid errors to hold.  By contrast, Ivanovic has advanced uneventfully in performances that also have displayed her progress since last year, mostly regarding her confidence.  While Stephens shoulders the burden of making adjustments against a former nemesis, Ana bears the pressure of repeating a result that she already proved her ability to produce.

Fish vs. Simon:  Watching the American’s strange victory in the previous round, an observer might either have marveled at his comeback from a two-set deficit while dropping just five games in three sets or have wondered why he lost two sets in the first place.  When Fish unleashed his weapons with accuracy and poise, he comfortably outplayed Davydenko in every area of the game, but he continued to struggle on the most valuable points in key moments as he has throughout his career.  The man who held his nation’s top ranking not long ago has reached the quarterfinals just once at his home major, flinching from the spotlight when it shines upon his unassuming personality.  Under the bright lights of Ashe, Fish must find a way to embrace an atmosphere that does not feel natural to him, for he cannot shrink from an aggressive mentality and expect to outlast the indefatigable Simon.  A clay-courter at heart if not in reality, it appears, the Frenchman habitually numbs the minds of his opponent with endless rallies built upon his retrieving skills and endurance.  This type of challenge has troubled Fish before, although he won their only previous North American meeting in Cincinnati.  The key to his success there, the fast court allowed him to exploit the difference in explosiveness between their serves and start a significant percentage of points from an attacking position inside the court.  On a similar surface here, he likewise should press his advantage as soon as possible rather than letting Simon maneuver the rallies into neutral positions.

Murray vs. Lopez:  Less than enticing is the tennis component of this match, the sixth in a rivalry that has featured nothing but victories by Murray.  The Scot has lost one total set in those three previous matches, including a 25-game rout in the same round here a year ago, during which the veteran’s net-rushing proclivities tossed him into the teeth of his opponent’s greatest strengths:  return of serve and passing shots.  But the comically open affection of his mother, Judy, for the aquiline Lopez adds an entertaining subtext to this encounter for viewers seeking a beguiling rather than dramatic afternoon.

Querrey vs. Berdych:  Like Jankovic, the Czech surely feels thankful for deciding to add a tournament in the week before the US Open to his otherwise arid summer.  A finalist in Winston-Salem after he took a wildcard to the event, Berdych has brought that quiet aura of confidence to two straightforward triumphs in New York.  Four years ago, Querrey ended his campaign here at the first hurdle in a startlingly lopsided victory that raised questions regarding his opponent’s commitment level.  Ironically, parallel questions have dogged the American for much of a generally underachieving career, which has featured three Los Angeles titles and little else of note.  Sometimes too relaxed for his own good, this Southern California native has matured during his extended injury hiatus and now approaches his matches with more thoughtfulness as well as a little more purpose.  A strong Wimbledon effort augured well for Querrey’s fortunes at a tournament where he can expect vigorous crowd support, from which he clearly draws energy.  On the other hand, he displayed very little energy in an unsightly loss to Berdych a week ago in Winston-Salem, struggling to hold serve and growing frustrated too easily as he had in the past.

Cilic vs. Nishikori:  Not especially interesting on paper, this match intrigues because it reprises an interminable, sweltering encounter between these two men at the 2010 US Open.  Although Cilic had dictated the majority of rallies early in that match, Nishikori gradually chipped away at him until the lanky, brittle Croat crumbled in exhaustion during an anticlimactic final set.  Both have carved out  a modest existence in the second tier despite occasional bursts onto the tennis radar, such as an Australian Open quarterfinal (Nishikori) and a second-week appearance at Wimbledon (Cilic).  Whereas the Japanese star probably has reached the upper limits of his potential, his rival tomorrow has not accomplished as much as one would have expected from him a few years ago.  In a sport where careers end so swiftly, Cilic cannot afford to lose much more time in regaining his original path.