While Serena and Cilic seem to enjoy exceptionally accommodating paths to the quarterfinals, the other matches on Monday deserve more attention.  Who will labor the most on the national holiday?

Ivanovic vs. Pironkova:  Blocked from reaching the quarterfinals of a major for more than four years, the 2008 Roland Garros champion has collided in fourth round after fourth round with champions from the Williams sisters and Clijsters to Azarenka and Kvitova.  In this US Open beckons a far more inviting opportunity, for Ivanovic now finds her path barred by the relatively unintimidating Tsvetana Pironkova.  Best known for her success against grass, the Bulgarian never had reached the second week of the US Open before, and her marquee wins to date have reflected a curious mastery over Venus but no other elite contender.  Since Ivanovic’s last appearance in a major quarterfinal, however, Pironkova has reached that stage twice at Wimbledon in 2010 and 2011.  She also defeated Ivanovic in their only meeting, on the clay of Rome weeks before the Serb claimed Roland Garros.  Considering that history, this match might hold more drama than their comparative credentials suggest.  Against the unseeded counterpuncher’s stingy defense, Ivanovic cannot afford to spray unforced errors as liberally as she did against Stephens.  On the other hand, her fortitude in crafting a comeback from an early deficit in the third round should stand her in good stead, for the tenacious Pironkova will aim to test her patience and expose her movement.  If Ivanovic can harness her intense desire to halt this quarterfinal drought productively, she should thrust her opponent onto the defensive before the rallies even develop.

Federer vs. Fish:  Although the American stunned the greatest man ever to hold a racket at Indian Wells in 2008, he has lost all seven of their other encounters and has not benefited from the home-court advantage in four other American meetings.  But Fish has won sets from Federer on several occasions, including a tense Cincinnati final two years ago and another at the year-end championships last November, admittedly a dead rubber.  When he locates his first serve with both pace and variety, he can punish the Swiss master’s dwindling returning skills and capitalize on the openings that ensure by charging the forecourt, where he can take further time away from his opponent.  Federer has looked more agile and alert over the last several months than he has in two or three years, though, perhaps invigorated by the confirmation that he still can win majors in his fourth decade.  For his part, Fish has played a diminished schedule this season amidst serious injury fears, and a second straight appearance in the second week of a major represents an accomplishment as impressive as he could have hoped.  Never a fierce competitor at heart, he probably will accept the inevitable without undue struggle.

Murray vs. Raonic:  The most compelling match of the day on the men’s side, this match will become the second straight night session to feature one of the ATP’s towers of power.  Improving his form with each round, Raonic looked far more convincing in a straight-sets demolition of Blake than in a five-set battle with Giraldo across which he strewed 15 double faults.  Only a prodigious serving performance can carry him past Murray, who specializes in blunting the power of one-dimensional servers with penetrating returns and rapier-like reflexes.  Nevertheless, this fast court should add Raonic’s cause, as it did the fortunes of the much less formidable Lopez during an extremely tight four-setter against the gold medalist.  Also falling to Cilic at the 2009 US Open, Murray needs to curb his inner negativity while concentrating on dominating behind his own serve.  He won all three of the tiebreaks that he played against Lopez a round ago, so he should bring ample belief to those that likely will arrive here.  Content to rally from well behind the baseline on return games in the first three rounds, Raonic will need to step further into the court to create pressure on Murray.  To finish points, he will need to aim closer to the lines than usual on his first groundstroke after the serve, as he did when upsetting the Scot on the clay of Barcelona.  His execution on that shot, as crucial as the serve itself, over the course of five sets will decide whether he can threaten Murray here.

Almagro vs. Berdych:  More like one of the WTA catfights than the genteel ATP rivalries is this clash between two men who have lost little love for each other.  In the same round of the Australian Open, Almagro struck a ball directly at Berdych in the forecourt from which the Czech inferred malicious intent.  After conquering the Spaniard, he refused to shake hands with him in a gesture of disdain for the earlier incident, completing a sequence that interestingly resonated more with the older than the current generation of players.  (To this observer, neither man acquitted himself with much honor.)  At Indian Wells, Almagro earned his revenge over his accuser on the surface least favorable to him, only to see Berdych regain the ascendancy in Rome on the surface least favorable to him.  Just five notches apart in the rankings, they have established that either can defeat the other anywhere, and the escalation of tension between them has coincided neatly with a sudden increase in the frequency of their encounters.  Rallying from losing the first set to Querrey, Berdych displayed a firmer competitive resilience than usual in patiently breaking down the American.  When he fuses that resilience with his savage groundstrokes, surges can happen like his runs to the Miami and Wimbledon finals in 2010.  Meanwhile, Almagro showed some patience of his own in outlasting home hope Jack Sock during an unexpectedly tense third-round meeting, so expect both men to enter the court with all guns blazing. 

Kerber vs. Errani:  On the slow hard court of Hobart, the German crushed the future Roland Garros runner-up this January before Errani avenged that setback at her breakthrough tournament.  Well outside the fringes of relevance a year ago, both women have catapulted from a single stunning result at a major into the top 10 and international renown.  Comfortable everywhere on the court is the Italian, whom one can expect to drift towards the net to exploit Kerber’s habitually deep positioning behind the baseline.  Each of them has compiled a reputation as a counterpuncher, although each has demonstrated the ability to attack when the opportunity presents itself.  In general, Kerber and Errani aim for a clean, high-percentage brand of tennis that forces foes to construct points meticulously.  Fresh from a finals appearance in Cincinnati, the German brought substantial momentum to this fortnight, and her achievements there may have catalyzed a valiant effort against Venus in the most exciting women’s match of the tournament so far.  Advancing less eventfully, Errani has dodged a few bullets from challengers whom she should have outclassed more comfortably, but her puny serve (perhaps the worst in the top 20) and small frame force her to work harder for each victory.

Vinci vs. Radwanska:  Somewhat similar to the match before it is this meeting between an Italian and one of the WTA’s premier defenders.  Whereas Kerber has honed a more straightforward brand of consistency, Radwanska has turned counterpunching into an art form filled with nuance and subtlety.  Her deft gambits require a different sort of precision from the ferocious shot-making that defines the WTA, but her talents deserve no less admiration.  After an outstanding first half, the best span of her career to date, the Pole’s results have declined a little as a shoulder injury has hampered her.  Alternating solid with shaky in the first week, she probably lacks the energy to proceed a round further than she did at Wimbledon or to equal that result.  Radwanska has won all four of her encounters with Vinci, however, overcoming an opponent with a playing style similarly based around dexterity and timing.  Winning the Dallas title days before she traveled to New York, Errani’s doubles partner has found crisper form in the second half than the first half, the opposite of the second seed’s trend.  On the anomalous blue clay of Madrid, she did contest a tight two-setter with Radwanska earlier this year, and this match likewise should feature its share of suspenseful moments—as well as its share of service breaks.  Together with the prequel featuring Errani, these two women’s matches on Armstrong should combine for a beguiling afternoon after the intensity of Almagro vs. Berdych.