A hard-throwing fastballer, Dennis recorded a 1.47 earned run average for the Triple-A Jacksonville Suns in 1965 before being called up to the Cardinals in the midseason.

The next year he went 4–2 in 38 games, including one emergency start, but his ERA dipped to 4.98.

In a two-season career, Dennis posted a 6–5 record with a 3.69 ERA and eight saves in 79 games.

Dennis died of cancer in Fort Scott, Kansas, at age 65.

This biographical article relating to an American baseball pitcher born in the 1940s is a stub.