A hard-working and ambitious forward, Piątek was the top scorer for Polish first division vice-champions AKS Chorzów in 1937 and went on to lead the league the following season with 21 goals.

He scored twice in Poland's 4–0 win over Yugoslavia in a World Cup qualifier and took part in the legendary 1938 FIFA World Cup match against Brazil in Strasbourg, France on 5 June 1938, which Brazil won 6–5.

Piątek also scored a goal in the last international match played in Poland before the outbreak of World War II, a 4–2 victory over Hungary on 27 August 1939.

Piątek signed the Volksliste (German Nationality List) after the Nazi invasion of Poland during World War II which allowed him to continue his footballing career.

His club AKS Chorzów was now playing as Germania Königshütte, and with Piątek as their key player, the team dominated the first division Gauliga Schlesien – part of the German football league system – throughout the early 1940s far outperforming state-supported rivals 1.