Kemp, who was promoted to Triple-A Fresno on June 11, is off to a torrid start, hitting .357 with nine RBIs in his first 14 games. In 50 games at Double-A Corpus Christi before the promotion, Kemp hit .358 with 69 hits and 19 RBIs.
Appel, who was promoted to Triple-A Fresno on Wednesday, was 5-1 with a 4.26 ERA in 13 starts at Double-A Corpus Christi. He's currently MLB.com's No. 10 right-handed pitching prospect and the top Astros prospect after Carlos Correa's promotion earlier this season. Appel is set to make his Triple-A debut on Saturday when Fresno travels to Reno.