Listed at 5 feet 9 inches (1.75 m) tall and 165 pounds (75 kg), he was nicknamed "Peanuts" or "Gulliver."

Lehner's professional baseball career began when he was 25, after World War II service in the United States Army Air Forces.

He reached the majors in 1946 with the St. Louis Browns, spending four years with them before moving to the Philadelphia Athletics in 1950.

He started 1951 with Philadelphia, then was part of successive trades between the Athletics, Chicago White Sox, Browns, and Cleveland Indians.

His most productive season came in 1950 with Philadelphia, when he posted career-highs in batting average (.309), home runs (9), and RBI (52) in 114 games.