Trained in the youth ranks of
Hammarby IF, Werner made his debut in
Allsvenskan, the domestic top tier, for the club in 1971, at age 17. Hammarby reached the final of
Svenska Cupen in
1977, the main domestic cup, but lost 0–1 to
Östers IF. The highlight of Werner's career came in
1982 when Hammarby finished second in the table, going unbeaten the whole season. In the following playoff to decide the Swedish champion, the club went on to beat
Örgryte in the quarter-finals and
Elfsborg in the semi-finals. In the finals against
IFK Göteborg, Hammarby won 2–1 in the first leg away, but lost 1–3 in the home game at
Söderstadion to a record crowd, missing out on the gold medal. Throughout his time at Hammarby, Werner went on trial with German giants
Bayern Munich and reportedly attracted interest from
Standard Liège,
Kaiserslautern and
Toronto Blizzard. ==International career==