Griffin struggled through three minor league seasons before going 11-10 for Houston in 1969, winning TSN NL Rookie Pitcher of the Year honors. He struck out 200 batters in 188 innings. On April 19, 1970, he one-hit the Padres, but slipped to 3-13 and spent time in Triple-A. He battled back from arm trouble and worked mostly out of the Astros bullpen until late in 1973. On May 7, 1974, he one-hit the Pirates en route to a career-best 14-10 mark. A good-hitting pitcher, he managed 10 HR in 405 career at-bats.