Baseball officials say these young phenoms are the product of a shift in the baseball culture of the Dominican Republic. Thanks to more than a decade of investment by major-league teams, which have built players' academies there, and the growing sophistication of the network of scouts and player wranglers, known as buscones, Dominican pitchers are becoming more polished. In addition to the 94 mile-per-hour fastball that is standard equipment, Mr. Santana has two other major league-caliber pitches, while Mr. Volquez has three. Scouts say even Mr. Inoa, the 16-year-old prodigy, has a curveball and a change-up in addition to a blazing fastball.

"There is much more learning and teaching than ever before" in the Dominican Republic, says Omar Minaya, general manager of the New York Mets.