On September 21, 1956, he was traded to the Kansas City Athletics with Jim Pisoni in exchange for Al Pilarcik and Art Ceccarelli.

The Athletics and New York Yankees were frequent trading partners in the late 1950s, and on June 15, 1957, Duren, Pisoni, and Harry Simpson were sent to the Yankees for Billy Martin, Ralph Terry, Woodie Held, and Bob Martyn.

He has been retroactively credited with saving 20 games in 1958, the high mark in the American League that year.

In those days, the Yankee bullpen was a part of the short-porch right field and only a low chain link fence served as the boundary.

When called upon by Casey Stengel to relieve, he would not use the gate, but preferred to hop the fence with one hand and begin a slow walk to the mound with his blue Yankee warm-up jacket covering his pitching arm; he followed this routine even on the hottest days.

When he finally took the ball and began his warmups, the first pitch was sometimes a hard fastball 20 feet over the catcher's head.

[3] Shortly after being traded to the Angels, he struck out seven successive Red Sox batters, then an American League record.

[6] Duren was the inspiration for the character Ricky "Wild Thing" Vaughn in the movie Major League, according to its author and director David S.