Novak Djokovic is barely past his 21st birthday but is already dodging the bullets from the next bunch of young guns aiming to shoot their way to the top.
Although the world No 3 took his place in the fourth round of the US Open here on Sunday night, he did so only after surviving a near four-hour barrage of winners from Marin Cilic, the latest boy-giant to emerge from Croatia.
Djokovic won 6-7, 7-5, 6-4, 7-6, but 19-year-old Cilic served notice of his emerging talent. Fresh from winning his first ATP title at New Haven a fortnight ago, the world No 24 played with the assurance of a veteran of night matches in front of 23,000 capacity crowds here in Arthur Ashe Stadium. Attacking at every opportunity, Cilic hit 19 aces and 47 winners, even if the ultimately decisive statistic was his tally of 65 unforced errors.
Cilic is one of three teenage men who have made a particular mark on this tournament. The other two, 18-year-old Kei Nishikori and 19-year-old Juan Martin del Potro, were meeting yesterday evening for the right to play in the quarter-finals against Andy Murray or Stanislas Wawrinka, who were featuring in the showcase night match.
Asked how he felt about the next wave of players, Djokovic said: "Considering what I have been through all these years, I feel a little old, like I played tennis all my life, but it's good for the sport to see new teenagers and rising stars coming up – a couple of really tall guys, Cilic and Del Potro, and Nishikori. They're all top 10 players. I'm sure we're going to see them in the future."
Like his fellow countrymen Goran Ivanisevic, Ivan Ljubicic, Mario Ancic and Ivo Karlovic, Cilic uses his physical attributes to full advantage. At 6ft 6in tall, his serve is a particularly damaging weapon. His groundstrokes are struck with similar power, while his net play suggests he could be a force at Wimbledon in future years.
"The thing which surprises me a lot with his game is his movement," Djokovic said. "He's very tall and when you look at him physically and the way he walks you wouldn't think he had great co-ordination, but on the court he looks great. He's also improved his serve a lot. He can use his height and really rip that serve."
Djokovic, nevertheless, is a ferocious competitor and dug in for a lengthy battle after a first set that took more than an hour. Both players saved set points before Cilic won the tie-break 9-7.
The second set was equally tight until Djokovic turned up the pressure at 5-5 to make the decisive break and served out to level the match. The Serb's sheer consistency wore Cilic down in the third set, but the Croat made a fight of it in the fourth, saving two match points when Djokovic served at 5-4. However, he was never in the tie-break, which he lost 7-0.
Djokovic, who now plays the Spaniard Tommy Robredo, believes having a hard contest at this stage of the tournament could be beneficial. "Last year I had a match against Stepanek which was really extremely difficult, but I reached the finals. Hopefully, it could be the same this year."
He added: "I've always managed to get through those tough matches. I've lost some, but I've won more. The bottom line is that everybody's playing great tennis and is very fit physically, but if you're mentally able to play the best tennis in the most important moments then you're different to the others."
The bottom half of the men's draw is heading for some heavyweight confrontations. In the quarter-finals Djokovic is on course to face Andy Roddick, who swept aside Andreas Seppi, while Roger Federer will meet Nikolay Davydenko, provided they win their fourth-round matches against Igor Andreev and Gilles Muller respectively.
In the women's singles, Elena Dementieva will play Patty Schnyder in the quarter-finals after dropping only five games to beat China's Li Na. In the semi-finals the Olympic champion could play Serbia's Jelena Jankovic, who first has to dispose of Sybille Bammer. At the age of 28 the Austrian reached the last eight of a Grand Slam tournament for the first time by beating Marion Bartoli.