Brandon Morrow is the future of a shaky Seattle Mariners pitching staff, a 24-year-old phenom with a bazooka arm that fires 98-mph fastballs and sliders in the high 80s. Morrow also famously developed a diving curveball in the minors that last year held the New York Yankees hitless for almost eight innings. But perhaps the biggest curveball in Morrow’s life had him on the receiving end.

In 2003, Morrow was a high school senior with major league stuff that blew away hitters and scouts alike. But then he started feeling fatigued. His eyes would unexpectedly blur, he lost weight, his performance dragged, and his future seemed suddenly in jeopardy. During conditioning one day, Morrow mentioned his symptoms to a teammate, who happened to have done a research project on diabetes. He urged Morrow to see a doctor. When Morrow did, his blood glucose was so high that he was immediately hospitalized—and diagnosed with type 1 diabetes.

With insulin and a new diet, Morrow became the comeback kid of Rohnert Park, Calif., about an hour north of San Francisco. And in 2006, the Mariners drafted Morrow out of the University of California–Berkeley in the first round. Last season, as a relief pitcher, Morrow posted a 1.47 earned run average with more than a strikeout per inning, one of the few bright spots on a team that finished last in its division. Morrow has always been pegged as a future ace starter, but after spring training this April, he asked to stay in the bullpen, disappointing many Mariners fans. Still, Morrow’s electric stuff will be put to good use as the team’s new closer, and he says that pitching in relief makes it easier to manage his blood glucose, making him more effective on the mound.

Though Morrow, a 6-foot-3, 195-pound righthander, is a potentially dominant force in the high-pressure role of closer, many baseball fans still view him as a youngster learning the ropes. But Morrow has taken on another level of responsibility. In an unexpected twist, fellow Mariner reliever Mark Lowe was diagnosed with diabetes last year. Now Morrow is helping Lowe cope with the news and change his diet. In short, the young fireballer has become something of a seasoned veteran and personal coach—on the fine art of being a professional athlete with diabetes.