Butler spent the entire 2010 season with the Batavia Muckdogs of the New York–Penn League. Despite an 0–3 win-loss record, he led the league's relievers with 14.67 strikeouts per nine innings pitched, notching 50 strikeouts in 30+2⁄3 innings of work.[5] In 2011 Butler again found himself splitting time between teams. He started the season with the Quad Cities River Bandits, pitching 15+1⁄3 innings in 12 games allowing just two runs while striking out 16 batters before advancing to the Palm Beach Cardinals.[5] At Palm Beach he shut down opposing offenses, striking out 52 batters and posting a 1.25 ERA as he picked up 17 saves. The numbers earned him post-season honors as the Cardinals 2011 Minors Reliever of the Year by The Cardinal Nation/Scout.com and 2011 Palm Beach Cardinals Relief Pitcher of the Year.[5] After the regular season Butler was chosen by the Cardinals to play in the Arizona Fall League for the Peoria Javelinas[5]
Keith Butler spent the entire 2012 season with the Double-A Springfield Cardinals. He earned Texas League mid-season and post-season All-Star honors.[5] Butler had 25 saves while posting a 5–1 win-loss record and a 2.76 ERA in 53 relief appearances.[6] Following the season, Butler was added to the Cardinals' 40-man roster to protect him during the Rule 5 draft.[7]
Major leagues
On May 31, 2013, Butler was promoted to the major leagues for the first time.[2] He made his major league debut on June 1 against the San Francisco Giants at Busch Stadium, giving up one hit, one walk, and striking out one in a single inning of work. The next day, Butler pitched a perfect ninth inning for the Cardinals.[8] Butler made 16 appearances for St. Louis during his rookie campaign, recording a 4.05 ERA with 16 strikeouts over 20 innings of work.[9]
Butler appeared in two contests for the Cardinals in 2014, but allowed six runs on six hits with two strikeouts over two innings of work.[10] On May 24, 2014, it was revealed that Butler would require season-ending Tommy John surgery to repair a tear in his right ulnar collateral ligament.[11] On November 18, Butler was removed from the 40-man roster and sent outright to the Triple-A Memphis Redbirds.[12]
Butler split the 2015 campaign between Memphis and Palm Beach, accumulating a 2-3 record and 5.28 ERA with 36 strikeouts and two saves in 44+1⁄3 innings pitched across 37 appearances.[13] He elected free agency following the season on November 6, 2015.
