Lee Duck-hee, 18, is among the best tennis players on the planet, but that’s not the only reason he’s exceptional. The South Korean, currently ranked 136th in the world, is also deaf. In pro tennis, where the speed of a serve can reach 150 miles per hour, hearing the ball enables faster reactions. A delay of even the tiniest fraction of a second could decide a match, which makes Lee’s success even more remarkable. Although most studies suggest Duck-hee’s condition leaves him at a distinct disadvantage in tennis, others think his disability could actually help explain his success. “When one sense is compromised, other senses are heightened to compensate,” says Paige Stringer, a former member of the U.S. Deaf Olympics tennis team. “People who are deaf or hard of hearing may have an advantage in tennis because they can [better] pick up visual cues.”