Alvarez, 24, is 8-5 with a 2.48 ERA and 1.22 WHIP in 22 starts and 137 2/3 innings this year. He leads baseball with three shutouts and was a deserving first-time All-Star this summer.
The Marlins called up lefty Dan Jennings to fill the roster spot. The 27-year-old has a 2.47 ERA in 91 relief innings with Miami over the past three seasons.
Righty Jacob Turner will replace Alvarez in the rotation. Turner, 23, has a 5.69 ERA in 74 1/3 innings across 11 starts and eight relief appearances in 2014.