Nicknamed "The Monster", the 6 ft 6 in (1.98 m), 230 lb (100 kg) right-hander had a scorching but short-lived period of dominance for the Boston Red Sox in the early 1960s.

[3] He was a star basketball and baseball player at Michigan State University before signing with the Red Sox as an amateur free agent in 1959.

[3] Originally a starting pitcher when he began his professional career, Radatz compiled a 16–10 record and 3.48 earned run average in his first two seasons in the Red Sox farm system.

[6] He went on to lead the American League in saves (24), games (62) and relief wins (9), while posting a 2.24 ERA in 124.2 innings his rookie season, earning the AL's Fireman of the Year by The Sporting News.

[3][7] Yankee manager Ralph Houk, who said, "For two seasons, I've never seen a better pitcher,"[8] added Radatz to his 1963 AL All-Star squad after a 33 scoreless inning streak[3] saw his ERA dip to 0.88 on June 14.

Most notably, he fanned 181 batters in 157 innings, setting a record that still stands for most strikeouts by a relief pitcher in a single season.

[13] He settled down, bringing his ERA down to a far more respectable 3.91 and earning 22 saves by season's end, but his 9–11 mark was the first losing record he had posted in his major league career.

[15] Radatz was mentioned in trade rumors with the Los Angeles Dodgers, Milwaukee Braves and Minnesota Twins during the off-season, but eventually returned to the Red Sox.

On June 9, Radatz pitched a scoreless ninth inning against the New York Mets at Wrigley Field to earn his first career win since September 14, 1965.

[19] He earned a spot on the major league roster out of spring training 1969, and was 2–2 with a 3.32 ERA in 11 appearances when his contract was sold to the Montreal Expos at the June 15 trade deadline.

Before his death in 2005, Radatz worked as pitching coach for the North Shore Spirit, an independent league team based in Lynn, Massachusetts.