Steffen started out as an amateur with Cantonal Neuchâtel and later became the first Swiss footballer to play in England when he signed for Chelsea.

He had only journeyed to England to learn the language, having been sent by his parents in preparation for him joining the family's fruit and vegetable business, but his teacher turned out to be the wife of then-Chelsea manager, Billy Birrell.

Steffen was a cultured and dedicated full back, tall and pacy, who quickly became a crowd favourite at Chelsea, while his blonde hair and good looks also won him admirers.

Steffen returned to Switzerland at the end of the season to finish his national service and was made club captain in his final game for Chelsea, also against Derby.

He also played in a 1–0 win over an England side containing Stanley Matthews, Tommy Lawton and Billy Wright in Zurich in 1947.