In the following year, he returned to the mound, this time making his debut on American soil with the short-season Single-A Lowell Spinners. In 15 starts, Sánchez posted a 3–4 record with a 1.77 earned run average (ERA), and by the end of the year was widely considered one of Boston's top pitching prospects. After the 2004 season, Baseball America named Sánchez Boston's fifth-best prospect, behind shortstop Hanley Ramírez, outfielder Brandon Moss, and pitchers Jonathan Papelbon and Jon Lester. By 2006, Ramírez, Papelbon, and Lester had all played in the majors; Moss was selected as the Portland Sea Dogs most valuable player in 2006.