He's out of the Bronx by way of Ghana, just 15 and bamboo thin, but he serves 120 mph. Top pros, including John McEnroe, have trouble dealing with his forehand and he's got flash-fast feet. Fact is, the kid, Selifu Mohammed, split sets with McEnroe when they played a few weeks ago, sending Mac into several of his trademark tirades. "He's got tremendous feel for the game," McEnroe graciously said later. "He has the tools, he can do good things." So the buzz about the teenager is getting out a little bit in local tennis circles. For Selifu, shy, with a wide lopsided grin, could develop into the biggest tennis star to come out of the metropolitan area since Queens product McEnroe himself, followed more recently by James Blake, of Yonkers and Harlem, and now ranked 28th in the world. "I want it, to get into the top 20, top 10, why not," Selifu said softly after playing a practice match at the Columbus Tennis Club on 99th St. in Manhattan. "He can go all the way. He's got the ability, right now his forehand is world class," said Bruce Haddad, who informally coaches Selifu and is one the city's top teaching pros. But there are a lot of big ifs. If he learns to put together points strategically, if he has the mental toughness and if he can put more spin on his second serve. Then, for Selifu, there's the biggest if of all. Money. As in at least $250,000, or full sponsorship by the United States Tennis Association's junior development program or a top full-time tennis academy. That's the cost of creating a top 20 contender out of a 15-year-old with raw talent, according to Haddad, once the fourth-ranked 16-year-old in the U.S. The money goes to coaching and travel to the international junior tournaments, including the French and Australian Opens and Wimbledon. "You have to be in the top four or five in your country to qualify," Haddad said. "You have to travel, and travel and support is expensive." But Selifu is no rich tennis brat. His father, once a cook for John Rawlings, former president of Ghana, died just weeks ago. His mother has a business selling fruit in Accra, the capital of Ghana. As far as Haddad knows, the USTA has never even heard of Selifu. Selifu is living in the Bronx with his older brother and sister, who both teach tennis at the Stadium Racquet Club off Jerome Ave. Selifu is a sophomore at Taft High School, which does not have a team. And he's not eligible for the USTA development program because he's not a citizen. He doesn't even have a green card, and he's not eligible to play in the top junior tournaments in this country, where results could get him sponsorship or a scholarship to an academy like Nick Bolliteri's in Bradenton, Fla. "There are obstacles, no question," said Xavier Luna, another of the city's top teaching pros and the man who has taken Selifu under his wing almost from the day he arrived from Ghana three years ago. But Luna, Haddad and a small group of other New Yorkers are determined to help Selifu make it. His story, and their part in it, is as remarkable as his forehand. "I started playing tennis when I was 4, at the Accra sports stadium where my mom was selling fruit, and she wanted me near her, after school, and there are tennis courts there," he said. His older brother Yakubu, now 23, and his sister Alima, 19, had started playing before him. "I got serious when I was 8," he said. At 11, Selifu was a successful junior, but Ghana does not have a program that supports young players. First his brother emigrated here, then his sister, and when Selifu was 13, they bought him a ticket and he came too. Yakubu already had his job at Stadium and when Selifu showed up, Luna, who runs the junior program, immediately recognized his talent. At that point, Selifu and his siblings, both of whom are legal residents, were living with Luna, who has a wife and children of his own. "I helped them out" Luna said. "Why not?" Meanwhile, Selifu was playing in the junior program at Stadium and began entering local tournaments. By last year, he was winning adult tournaments, driven to events and helped by other families who play at the club. "It's not a big deal," said Meris Powell, one of those who donates her time. "I'm a substitute tennis mom." This summer, his tournament victory count hit 20. "Every day, I play from 6:30 to 7:30 before school," Selifu said. In July, he met Haddad. "I wanted to help him out, get him a little money," Haddad said. "I was injured so he helped me out with lessons, hitting with my students." "Then I saw him play some big matches. I was amazed," said Haddad, who arranged the session with McEnroe, and began coaching Selifu. "He literally gets better before your eyes," said Haddad. "The big question is where does he go from here?" About two weeks ago, the answers began to appear. One of the families helping out is in the process of adopting Selifu, so he can get his citizenship and play in the big tourneys. McEnroe has spoken to Bolliteri about him and there's a chance Selifu will get a full scholarship, worth about $55,000 a year, to Bolliteri's academy, which includes schooling. That's where Monica Seles, Andre Agassi and Jim Courier, among others, polished their games. "He's going to make it," Luna said. "I've coached the top national kids, sent them to UCLA and other top tennis schools and this kid is better than any of them were. Most important, he's fearless on the court, absolutely calm in every situation, which is rare for a 15-year-old."