He honed his baseball in the West Valley Little League before playing on the varsity team of Taft High School.

One scout saw potential in him in Tommy Lasorda, who saw ideal mechanics and arm action that seemed right for the majors rather than giving him a bad report.

He pitched 2+2⁄3 innings while allowing four runs (two earned) on five hits, and three walks while having three strikeouts; he was credited with the loss while starting his career with a 6.75 ERA.

He pitched a complete game against the Pittsburgh Pirates, allowing four runs on six hits as the Astros pulled a 5–4 win.

[5] On November 23, 1976, he was traded (along with Jerry DaVanon) to the St. Louis Cardinals for Bob Detherage and Joe Ferguson.

He garnered his last victory on July 1 with a seven-inning, five-hit performance while allowing only one run in a 3–1 win over the Chicago Cubs.

From 1979 to 1996, Dierker served as a color commentator on the Astros' radio and television broadcasts, a position he returned to in 2004 and 2005.

In 1995, Dierker alongside Pete Van Wieren called Games 1–3 of the National League Division Series between the Atlanta Braves and Colorado Rockies for The Baseball Network.

[8] On October 4, 1996, Dierker was hired as the twelfth manager of the Houston Astros, replacing Terry Collins.

[9] Doubts were raised over the potential for a first-year manager replacing a fiery predecessor, but Dierker won the trust of his players as being just one of them.

[10] Collins was reportedly dismissed due to disagreements with the two star players in Jeff Bagwell and Craig Biggio.

When Dierker was asked how he would approach them, he stated that they would not be a problem under his watch; he believed the statement helped him get the job and that it was false.

[13] The 1998 team, bolstered by a trade for Randy Johnson at the deadline, won 102 games to set a new club record.

Dierker believed strongly in his team's chances for 2000 despite the trades of Mike Hampton, Derek Bell, and Carl Everett.

[21] Dierker penned a book entitled This Ain't Brain Surgery, which detailed his baseball career as a pitcher and a manager.