The Rockies promoted Sullivan from High-A Spokane to Double-A Hartford on Saturday.
Sullivan made his Double-A debut later that day, working four scoreless innings and striking out two while allowing three hits and one walk. The left-hander was bumped up to Double-A after turning in two straight five-inning, 10-strikeout performances to end his time at High-A. Sullivan forged a 2.16 ERA, 0.84 WHIP and 101:8 K:BB in 83.1 innings with Spokane.