Americans of a certain age are old enough to recall a famous ad campaign from 1986 in which New York filmmaker Spike Lee teamed up with Michael Jordan to advertise the Nike brand “Air Jordan” basketball shoe. In these noted commercials, Lee’s character, hoops junkie Mars Blackmon, utters the memorable slogan, “It’s gotta be the shoes!”

As the years go by, that single utterance is gaining more and more traction in the world of big-time tennis.

Earlier this decade, Martina Hingis, before her withdrawal from the sport amidst a drug scandal, sued the Italian sportswear company Sergio Tacchini for making shoes that hurt her feet. In a sport where top players generally use one pair of shoes per match, it was alarming that an athlete and apparel provider could go to war in such a public manner.

Then again, if shoes don’t lead to comfort, perhaps we’ll see more litigation before too long. Just ask the top seed in the 2009 Australian Open, Jelena Jankovic.

After an easy 3-and-1 demolition of an overwhelmed opponent in the first round of this event, Jankovic advanced to the third round on Wednesday afternoon in Melbourne Park, but not before taking a surprising step backward in her pursuit of her first Grand Slam title. The 23-year-old from Belgrade, Serbia, managed to defeat Belgian’s Kirsten Flipkens in straight sets, but not before laboring for nearly two hours in the pounding summer sunshine of the land Down Under. On the same day that No. 3 seed Dinara Safina was surprisingly extended to a third set in her own second-round match, Jankovic had a chance to send a statement to every other competitor in the top half of the women’s draw, which is widely regarded as the wide-open half of the field. Instead, Jankovic was happy to merely live for another day. The 6-4, 7-5 win–achieved in 1 hour and 46 minutes–will reduce Jankovic’s stature as this tournament continues. The middle rounds beg for more than simple survival–the world No. 1 has to get her mojo back, and she’ll need comfortable shoes to do so.

Jankovic looked great in the first round, but it bears mentioning that the Serbian star said in her post-match press conference that her feet experienced a burning sensation on the Plexicushion hardcourt surface. Apparently, that fiery feeling only intensified in round two, enough to force Jankovic to poke at her feet on dozens of occasions throughout the match. Discomfort–if severe enough–will inevitably prove to be a distraction, and distracted is exactly how Jankovic played against Flipkens, who hit a hard ball and accumulated more winners (30 to 21) on the afternoon.

How was Jankovic able to triumph? For one thing, Flipkens’s 30 winners paled in comparison to her 38 errors. As was the case in the first-round match between Ana Ivanovic and Julia Goerges, this Jankovic-Flipkens fistfight was decided more by the erratic play of the unknown underdog than any spectacular displays from the Serbian favorite. A 6-2, 6-1 win represents complete domination, but a 4-and-5 victory reflects an ability to dig out the key points, and that’s what Jankovic did in Hisense Arena. The final three games of the second set told the tale in a consistently tight affair.

In the first nine games of set two, Jankovic accumulated only 6 winners, a rather shocking statistic for a top-seeded player in an early-round match at a slam. Jankovic blasted winners against Yvonne Meusburger in round one, but on this day, the shoes–and her overall movement–took away her power hitting and her confidence. Flipkens couldn’t close the deal in set one, but late in the second stanza, the Belgian carved out a 5-4 lead and had her heavily-favored opponent in a bit of trouble. Given her shoe problems, Jankovic didn’t want to contend with a third set, which would only worsen her situation and cause a lot more strain on her body. Real drama entered a match that had figured to be a cakewalk.

Roughly 15 minutes later, the drama would be over.

Jankovic had looked exhausted earlier in the set, and had been unable to retrieve shots the way she normally does. Serving at 4-3 in the second set, Jankovic stood around instead of sprinting as a Flipkens forehand ticked high off the tape and landed in the ad court service box. A healthy Jankovic would have tracked the ball down and returned it for a winner, but this tired and distracted player barely attempted to pursue the shot, and as a result, Jankovic conceded the break that enabled Flipkens to make her move. But just when all seemed grim for Jankovic, the top seed found a second wind and a new dose of determination.

Partly irritated by past lapses and partly motivated to get off the court as quickly as possible, Jankovic turned into a different player once Flipkens gained the 5-4 advantage. Suddenly running down balls once again, the superb defensive player won 10 of the last 12 points to win three straight games with relative ease, and head to the locker room with a sigh of relief. After the paltry total of 6 winners in the first nine games of the set, Jankovic–due to her regained retrieval skills–hit 5 winners in those final three games, mostly on running passing shots after all-court rallies.

Disaster had been temporarily averted, but as this tournament moves forward, Jankovic knows that her status as a championship contender has taken an appreciably large hit.

It’s gotta be the shoes.