Walden was born November 16, 1987, in Fort Worth, Texas, and graduated in 2006 from Mansfield High School.

While playing for the amateur league team D-BAT Mustangs of Carrollton, Texas, he was teammates with future fellow MLB pitcher Clayton Kershaw.

[6] When the Angels traded Brian Fuentes to the Minnesota Twins on August 27, 2010, they began to use Walden as their setup pitcher in his place in the eighth inning.

[12] On July 7, Walden was selected to appear in the MLB All-Star Game for the first time, taking the place of an injured Mariano Rivera.

[18][19][20] On November 30, 2012, the Angels traded Walden to the Atlanta Braves in exchange for pitcher Tommy Hanson.

[23] On November 17, 2014, the Braves traded Walden and Jason Heyward to the St. Louis Cardinals in exchange for Shelby Miller and Tyrell Jenkins.

[29] The Cardinals initially estimated a timetable of six-to-ten weeks before he could return to pitching,[30] but recovery took much longer than expected.

[33] After sustaining a grade 2 latissimus dorsi muscle strain, the Cardinals placed Walden back on the disabled list to start the 2016 season.

[35] The Braves and Walden mutually agreed to void his contract on February 9, 2017, after discovering that his rehab had not been progressing as expected.

His off-speed pitches worked extremely well in tandem with his fastball, with whiff rates of about 48% on his changeup and 61% on his slider — each well above the league averages.