On September 6, 2012, Scahill was selected to the 40-man roster and promoted to the major leagues for the first time.[3] In six appearances for Colorado during his rookie campaign, Scahill recorded a 1.04 ERA with four strikeouts across 8+2⁄3 innings pitched.[4]
Scahill made 23 appearances for Colorado during the 2013 campaign, registering a 1-0 record and 5.13 ERA with 20 strikeouts across 33+1⁄3 innings pitched.[5] He pitched in 12 games for the Rockies in 2014, logging a 1-0 record and 4.80 ERA with 11 strikeouts over 15 innings of work.[6]
Pittsburgh Pirates
On November 11, 2014, Scahill was traded to the Pittsburgh Pirates in exchange for Shane Carle.[7] He made 28 appearances for Pittsburgh during the 2015 season, compiling a 2-4 record and 2.64 ERA with 24 strikeouts across 30+2⁄3 innings pitched.[8]
Scahill pitched in 15 games for the Pirates to begin the 2016 season, recording a 4.41 ERA with 13 strikeouts over 16+1⁄3 innings of work.
Scahill was designated for assignment by the Brewers on January 31, 2017, following the waiver claim of Ehire Adrianza.[10] He cleared waivers and was sent outright to Triple-A Colorado Springs on February 6.[11] On May 1, the Brewers purchased Scahill's contract, adding him to their active roster.[12] He was designated for assignment again following the promotion of Brandon Woodruff on June 13.[13] On June 30, Milwaukee added Scahill back to their active roster.[14] In 18 total appearances for the Brewers, he compiled a 1-3 record and 4.43 ERA with 10 strikeouts across 22+1⁄3 innings pitched. Scahill was designated for assignment for a third time on July 23.[15] He elected free agency on October 6.[16]
Chicago White Sox
On December 1, 2017, Scahill signed a minor league contract with the Chicago White Sox.[17] He began the season with the Triple–A Charlotte Knights, and was promoted to the major leagues on September 8, 2018. In six appearances for the White Sox, Scahill logged a 5.40 ERA with three strikeouts across five innings pitched. On October 26, he was removed from the 40–man roster and sent outright to Triple–A.[18]
Chicago Cubs
On January 18, 2019, Scahill signed a minor league deal with the Chicago Cubs. He was released on March 9, 2019.
