He plays rugby since 1991, when he joined the RG Heidelberg through the English Institute in Heidelberg. He played for the RG throughout his career, with the exception of spending a year in Ireland and playing for Old Wesley there. With RGH Weselek won twice the German 15er side championship, 4 times the German 7er side Championship in one time the German Pokal.
Weselek originally retired from the German national team after the Netherlands game on 26 April 2008, his 25th international, but returned to the struggeling German side for the game against Portugal on 27 February 2010.
Since 2012 he is headcoach of the Rudergesellschaft Heidelberg. Under his coaching the RGH won the German 7er side championship in 2015 and 2016. Weselek also coached the German unter 19 Team during the European championship in Portugal in 2015 where Germany endet up 5th place, a remarkable result