Along with right-hander Robin Roberts (a member of the Baseball Hall of Fame), Simmons was one of the twin anchors of the starting rotation of the "Whiz Kids", the Philadelphia Phillies' 1950 National League (NL) championship team.

[1] That spring, Simmons also pitched and played outfield in an All-American high school game between teams managed by Babe Ruth and Ty Cobb.

In 1949, Simmons returned to the Lehigh Valley, pitching for the Phillies in an exhibition match against the Allentown Redbirds, in front of a record crowd of 4,590 at Breadon Field in Whitehall Township.

The Phillies managed to hold off the Brooklyn Dodgers in the 1950 season's final contest on Dick Sisler's 10th-inning home run to win the National League again Simmons was stationed at Camp Atterbury and requested and was granted leave on October 4, 1950, to attend the Series.

Simmons signed as a free agent with the St. Louis Cardinals three days later, and began a comeback that culminated in 15- and 18-game-winning seasons in 1963 and 1964, respectively, while in a pitching rotation that included Bob Gibson and Ray Sadecki.

MLB Hall of Fame hitters Hank Aaron[4] and Stan Musial[5] each separately named Simmons as the toughest pitcher they had to face in their careers.