Tennis

The 6'9 1/2" Isner would lose the match, but he put a scare into the best player of the age, legitimized his dizzying rise (from No. 839 in June to the top 150) and showed he has more than one massive weapon. "Not just a guy who can serve," Federer said afterward. "He can do more, and I knew the danger."

Isner (below) wasn't acting alone. With 18-year-old Donald Young finally showing Grand Slam grit in his third-round loss to 10th-ranked Feliciano L�pez , the conversation about American men's tennis turned on a new question: Who has more upside?

Long the gifted prodigy, the compact (5'9", 145 pounds) Young has beefed up his serve to more than 130 mph. "It's a question of him getting comfortable on tour, getting stronger," says four-time Slam winner Jim Courier . "He's definitely top 20 material."

Courier says the same about Isner , 22, but he also describes Isner 's uncanny poise as "mind-bending" and adds that Isner 's serve will make him dangerous "until his arm falls off." Who will make the next big noise? For now, you've got to go with Big John.

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