Heilmann was known as a line drive hitter who clubbed the ball harder than any batter of his era with the exception of Babe Ruth. His one major handicap as a player was a lack of speed that led to his being known by the nickname "Slug". He was long known as "one of the slowest men in baseball." Hall of Fame sportswriter Tommy Holmes noted: "Heilmann was never much faster than an ice wagon on the base paths. Without doubt, he is the slowest moving great hitter who ever lived." According to Holmes, Ty Cobb's speed added 50 hits a year to his output, while Heilmann's lack of speed robbed him of infield hits. Sportswriter Harry Grayson later wrote that Heilmann's inability to beat out infield hits was the one thing that kept Heilmann from matching Rogers Hornsby as the greatest right-handed batter in baseball history.