A prolific goalscorer, he was successful in his country in the 1980s, and then had a career in Germany which spanned nearly 20 years, broken by a half-year stint in Switzerland. Leśniak started his professional career with Pogoń Szczecin, topping the Ekstraklasa goal charts in 1986-1987, for a final runner-up position. In 1988, he moved abroad, with Germany"s Bayer 04 Leverkusen, starting well (three Bundesliga goals in his first six games).
After a couple of solid seasons, Leśniak lost his importance in the side after the arrival of Ulf Kirsten, eventually leaving in 1992 to SG Wattenscheid 09, totalling 25 goals in three seasons.
He continued to play in the country until 2006 (aged 42), in various levels (from 2002-2005, he also acted as player-coach for SSVg Velbert). International goals.