Ken was born and raised in Albuquerque, New Mexico, and made varsity as a sophomore at Eldorado High School in 2007. His alma mater also sent pitchers Christian Parker and Kyle Weiland to the majors.
In 2016, Ken set a career high in strikeouts (102), becoming the sixth reliever in Astros history with a 100-strikeout season and the first since RHP Brad Lidge fanned 104 in 2006. He tied a career high and led the Astros with 69 appearances and tied a career high in saves (15), which also tied for the club lead. Ken posted a 13.98-strikeouts-per-9.0-innings ratio (102K/65.2IP), which ranked fifth in club history by a reliever for a single season. In just his second major-league season with the Phillies in 2015, Ken ranked third among National League relievers in ERA (1.80, 14ER/70IP), fourth in home runs per 9.0 innings (0.26, 2HR), tied for fourth in strikeouts (87) and eighth in strikeouts per 9.0 innings (11.19). On September 1, 2014 at Atlanta’s Turner Field, he retired Jason Heyward, Emilio Bonifacio and Freddie Freeman on 15 pitches in the eighth inning as four Phillies pitchers combined to no-hit the Braves, 7-0. It was the first combined no-hitter in Phillies franchise history.
Ken made his professional debut on August 20, 2011 for the Gulf Coast League Phillies and, in 2014, was invited to his first big-league spring training. After splitting the first two months of the season with Double-A Reading and Triple-A Lehigh Valley, he was called up to the Phillies and made his major-league debut on June 12 at Citizens Bank park, recording the final out of a 7-3 Phillies win vs. San Diego.