The Colorado Rockies selected Butler in the first round of the 2012 Major League Baseball draft. He signed with the Rockies, receiving a $1 million signing bonus. Butler made his professional debut with the Grand Junction Rockies of the Rookie-levelPioneer League, and was named an All-Star after going 7–1 with a 2.13 ERA and 55 strikeouts. Butler began the 2013 season with the Asheville Tourists of the Class ASouth Atlantic League, but after making nine starts for Asheville, he was promoted to the Modesto Nuts of the Class A-AdvancedCalifornia League. He was named to appear in the 2013 All-Star Futures Game, where he pitched an inning without allowing a run. Butler made six starts for the Tulsa Drillers of the Class AATexas League to conclude the season. The Rockies invited Butler to spring training in 2014. They assigned him to Tulsa to start the 2014 season, and he started Tulsa's season opener. After he pitched to a 2.49 ERA with 40 strikeouts and 19 walks in innings pitched, the Rockies promoted Butler to the major leagues for his debut on June 6. He recorded a loss in his first start, pitching 5innings and giving up 6 runs on 10 hits. He was placed on the disabled-list before his next scheduled start with right shoulder inflammation, and he was replaced by Tyler Matzek, who would be the third starting pitcher to debut for the Rockies in six days, along with Butler and Christian Bergman. Butler won the fifth starter's spot out of Spring Training in 2015. Butler struggled mightily at the beginning, inducing 30 walks while striking out just 29 in 54.1 innings. He was demoted at the end of May to AAA. Butler was once again called up, he finished the season with a 3–10 record along with an ERA of 5.90 in 16 games started. He also had his first complete game of his career. Right-handed batters had a higher batting average against him,.340, than against all other MLB pitchers in 30 or more innings. Butler finished the 2016 season 2-5 with a 7.17 ERA. On January 28, 2017, Butler was designated for assignment.
Chicago Cubs
On February 1, 2017, Butler was traded to the Chicago Cubs for James Farris. He made his Cubs debut on May 12 and pitched 6 shutout innings in a 3-2 victory over the Cardinals. Butler spent time in the Cubs rotation and in the AAA level, appearing in 13 games for the Cubs, 11 of them starts. In innings, Butler was 4-3 with a 3.95 ERA. The following season, Butler began the 2018 season in the Cubs bullpen before being placed on the 60 day disabled list.
Texas Rangers
On July 27, 2018, Butler was traded to the Texas Rangers in exchange for Cole Hamels. In 22 appearances, he pitched to a 6.47 ERA in 32 innings while going 2/2 in save opportunities. He elected free agency on November 21, 2018.
NC Dinos
On December 3, 2018, Butler signed a one-year, $800,000 contract with the NC Dinos of the KBO League. He was waived on July 3, 2019, after pitching to a 3–6 record with a 4.76 ERA in 13 starts.
