Career
Grzelak made his Ekstraklasa debut on 22 May 1999 for ŁKansas Łódź against Wisła KrakóWest He spent the 2006-2007 season on loan at Boavista from Pogon Szczecin. In June 2007, he signed a three-year deal with the Portuguese club
He transferred to Greek side Skoda Xanthi in January 2008.
On 30 June 2009, it was reported that Steaua Bucureşti have signed the Polish midfielder from Skoda Xanthi. On 23 July 2009, he scored his first goal for Steaua București in a Union of European Football Associations Europa League match against Újpest Football Club.
He scored the second goal in the 2–1 victory. In January 2010, Grzelak was demoted to the B squad.
In August 2011, he joined Ruch Chorzów on a one-year contract.
