Kei Nishikori’s 2008 US Open has been a truly memorable experience. Heading into this week, the 18-year-old from Japan had never before won a Grand Slam match. A few days later, he was in the third round against world No. 4 David Ferrer.

When he looks backs at this tournament down the road, Nishikori will always recall his maiden victory at a Slam against Juan Monaco. And he might even remember that he won his second-round match because his opponent was forced to retire. But surely, he’ll never forget his thrilling five-set win over Ferrer – 6-4, 6-4, 3-6, 2-6, 7-5 – under the lights at Louis Armstrong Stadium.

Nishikori took the initiative early on, hitting the ball with great pace and moving with the range fans expect from Ferrer. The fourth seed looked overwhelmed by his teenage opponent, and in just over an hour, he dropped the first two sets. Nishikori rode his forehand kill shot extensively, and, formulaically, the sets each ended 6-4.

But Nishikori quickly discovered that the rest of this match was not going to play out like the first two sets did. Ferrer epitomizes the label of a “grinder,” and he did well to uphold that reputation tonight. The Spaniard steadied himself in the third set, reducing his unforced errors and serving with aplomb (he won 73 percent of his first-serve points). When a running backhand passing shot earned Ferrer the first break of the set at 4-3, a switch flipped, making him a much more dangerous player. Ferrer held serve the rest of the way to win the set 6-3, and an entirely new match ensued.

Ferrer’s intensity escalated and could be felt throughout the stands. He continued to ride this surge, winning the fourth set comfortably, 6-2. Ferrer broke Nishikori in three consecutive service games to start the set, and he was never seriously threatened thereafter. A blistering forehand winner officially sent the match to a fifth set, and Ferrer’s confidence continued to build.

Against all logic, Nishikori looked calm and composed to start the final set. He suddenly played like he did at the start of the match, retrieving most anything Ferrer sent his way and striking the ball with renewed force. Quickly, he amassed a 5-2 lead.

But Ferrer, expectedly, did not go down without a fight. Needing to hold serve twice, as well as break Nishikori to stay alive, Ferrer did so, even saving a match point in the process. The crowd came to its feet after a Ferrer backhand that caught the line denied Nishikori a victory he desperately craved. The match was tied at two sets apiece and 5-all, and another new match had begun.

Nishikori again impressed with a confident hold to lead 6-5. Ferrer, not to be outdone, impressed when he saved a second match point with a clutch first serve. But it was Nishikori – and not his indefatigable opponent – who ultimately emerged as the winner. In a pressure-filled game, Nishikori’s backhand didn’t break down after repeated exchanges with Ferrer. When Nishikori earned his third match point, he struck a winner with his signature forehand that signaled his true arrival on a Grand Slam stage. Nishikori becomes the first Japanese player to ever reach the Round of 16 at the US Open.

Nishikori speaks limited English, but his loss for words during his on-court interview could be attributed to what just unfolded. “I still can’t believe it. I was playing great, he was playing great too,” said Nishikori. “I’m very tired but…I don’t know.”