Frank J “Lefty” Hoerst was born on August 11, 1917 in Philadelphia, Pennsylvania. In the 1930s, Hoerst was a standout basketball player at LaSalle College, serving as the team's captain and as its highest score.

He signed with Mayodan of the Bi-State League in 1939 and had an 8-9 won-loss record in 23 games. His major league debut came with the Philadelphia Phillies in April 1940, making six relief appearances and earning a win before joining Pensacola of the Southeastern League for the remainder of the season.

Hoerst was 16-7 with a 2.56 ERA for Pensacola and was back with the Phillies in 1941 making 37 appearances (11 as a starter) for a 3-10 record. In 1942 he made 33 appearances (22 as a starter) and had a 4-16 record with the last-placed club.

Hoerst entered military service after the season. He made the Murmansk run as a gunnery officer aboard the Cunard liner Queen Elizabeth in late 1942. He later served on the West Gotomska, a merchant ship in the Atlantic; the Cape Henry, a cargo ship which cruised to East Africa; the Mormac Dove, a Moore-McCormack Line army transport in the Pacific and the Artemis-class attack cargo ship USS Sappho (AKA-38).

Hoerst was back with the Phillies in 1946 and had a 1-6 record in 18 appearances. In 1947, he was 1-1 with the Phillies and 12-11 with Memphis of the Southern Association. He ended his playing days with Memphis in 1948 and became baseball coach at LaSalle College in 1950. He was later inducted into the LaSalle Hall of Athletes.

Lefty Hoerst passed away on February 18, 2000 in Mount Laurel, New Jersey.