Not too many top tennis players go unnoticed as youngsters. Roger Federer was the best junior in the world in his day. Andre Agassi was so much better than his peers that he moved into the pros at age 16. Pete Sampras’s talent, while ultimately underestimated, was seen as considerable. In women’s tennis, talent becomes noticeable at even earlier ages — many top women win major titles before they reach the age of 20. Martina Hingis, who retired last year, won her fifth and final major title four months after her 19th birthday.

Rather than overlook talent, those who watch tennis tend to overestimate or exaggerate it. Aaron Krickstein, Al Parker, Tommy Ho, Anna Kournikova are among those young players who were destined for greatness but barely left an impression on the sport. What, then, to make of Kei Nishikori, the Japanese teenager who defeated James Blake, the no. 12 player in the world, in the Delray Beach final two weeks ago to become the youngest player to win a tournament on the men’s tour since a 16-year-old Lleyton Hewitt in 1998? (He is also the first Japanese player to win a tour title since Shuzo Matsuoka in 1992.) Is Nishikori that rare thing in tennis, a talent who went unnoticed by most of the world?

Nishikori, 18, is from Japan, not Jupiter, so it’s not accurate to say that no one had heard of him before his victory in Delray Beach. But he is (or was) as much of an unknown as one will ever see in the tennis world. Nishikori had a decent junior career, finishing as high as no. 6. His best performance in the junior majors came in doubles, when he won the French Open junior title in 2006. He trains at Nick Bollettieri’s tennis academy in Florida but not on the full scholarship that many of the academy’s most promising students receive (Nishikori’s training has been paid for by Masaaki Morita, the retired CEO of Sony).

If Donald Young, the most talked-about player under the age of 20, had gone on a streak and won the Delray Beach tournament, it would have been surprising, but not nearly as much so, since Young was once the best junior in the world and has been “destined” for big things since childhood. No scout or coach in his or her right mind would have predicted that Nishikori would win a title before Young, and many of those same learned observers are skeptical that the adult Young, who like Nishikori is small and lacks an overwhelming serve, will do a whole lot of winning anytime soon, despite his improvement in the last year (Young and Nishikori played last year and Young won convincingly).

Last October, Nishikori lost 6–2, 6–0 in the second round of a tournament in Seoul, Korea, to Daniel Koellerer from Austria, then the no. 154 ranked player in the world. Less than four months later, he had beaten Blake and was playing his first match in San Jose last week when he saw Andy Roddick, the top ranked American, watching from the stands. Roddick’s visit seems to have had two purposes. He didn’t know anything about Nishikori and wanted to have a look before they met in the second round. He also wanted to play with the kid’s mind, as he continued to do so during their match last week. In one exchange at the net, Nishikori aimed at Roddick’s body — not uncommon and certainly acceptable — and Roddick taunted him for it, suggesting Nishikori ought to be more vicious next time and go for some skin. Nishikori, flustered, didn’t put up much resistance (he lost 6–2, 6–4). Roddick paid Nishikori a few compliments after the match and took pride in having taught the teen a little something about gamesmanship.

“I wanted him to think about other stuff and not how well he’s playing,” Roddick said. “He’s probably not that happy with me for doing that. But I don’t need any young friends.”

Nishikori has plenty of new friends at the moment — winning will do that for you. Is he going to convince them to become loyal followers? Though his size and serve are not ideal, he has a few things going for him, especially speed. Quick counter-punchers in the mold of Hewitt usually meet with early success, though they don’t hold up too well in the long run. Nishikori’s forehand packs enough punch and his backhand is steady. It’s easy to see him reaching the top 30 or 20, but it’s difficult to predict much beyond that. His colleagues on the tour certainly won’t underestimate him again — that alone could make the next few months difficult and discouraging.

If Nishikori does go far, we might one day say that he reminds us of the man he beat in his first final. Blake was a good junior, but not a heralded one — no budding tennis superstar bothers with college. Most people thought Blake’s older brother Thomas would be the better player, and no one predicted that Blake would become a top five player, which he accomplished in 2006. Heck, few people would have considered him a candidate for the top 20, which he reached for the first time in early 2006, at the age of 26, a time when tennis players usually begin to decline, not surge. Blake’s feats are rare, but he won’t be the last of his kind. Maybe Nishikori is next.

* * *

Maria Sharapova, the Australian Open champion, continues to dominate. The Russian won her second title of the year in Doha yesterday, running her record to 14–0 on the season (including the Federation Cup). She defeated Vera Zvonareva 6–1, 2–6, 6–0 (she lost eight points in the final set). Of interest: James Blake will play Donald Young in the first round of this week’s tournament in Memphis.

Mr. Perrotta is a senior editor at Tennis Magazine. H e can be reached at tperrotta@tennismagazine.com.