Rockies call up lefty Sean Sullivan for big league debut in Las Vegas

The Rockies are turning to another second-rounder to bolster their roster.

Colorado is promoting left-hander Sean Sullivan, who will make his major league debut Friday night against the Athletics in Las Vegas, per Kevin Henry of the Denver Gazette. Sullivan isn’t on the 40-man roster and a corresponding move has not yet been reported.

Sullivan, 23, was the Rockies’ second-round pick in 2023 and ranks as the organization’s No. 11 prospect, according to MLB.com. The 6-foot-4 lefty posted a 2.94 ERA across Single-A and Double-A last year but has scuffled to a 5.60 ERA in 11 Triple-A starts in 2026.

He’s not a power arm. Sullivan’s four-seamer sits just 89 mph, and he survives on command, a deceptive low three-quarters slot and a quality changeup. He walked just 6% of hitters in the minors a year ago.

The debut comes in a tough spot. The A’s are hosting their first two series in their soon-to-be hometown in Nevada, and the Pacific Coast League park plays as an extreme hitters’ haven. Oakland and Milwaukee combined for 29 runs and 11 home runs in the first MLB game there this week. Sullivan knows the place, too — he allowed seven runs on 12 hits over 4 2/3 innings in the same ballpark May 19, taking the loss for Albuquerque.

Sullivan follows fellow 2023 second-rounder Cole Carrigg, who debuted Tuesday, tripled for his first hit and then homered Thursday.