Krol, 27, played more than 100 games in the Polish first division, most notably with Jagiellonia Białystok, Polonia Bytom, Podbeskidzie Bielsko-Biała, and most recently with Piast Gliwice.
In 2012-2013, he helped FC Sheriff Tiraspol win the Moldavian first division title and Supercup.
Krol was loaned to the Chicago Fire in 2010, recording one assist in 19 games played, 17 as a starter, in his only season in MLS. He also played one game in the US Open Cup and two friendly matches against Paris Saint-Germain and AC Milan.
Earlier in his career, he spent two seasons with the reserve team of the prestigious Spanish club Real Madrid, in 2007 and 2008.
At the international level, Krol played for the Polish U20 national team, taking part in the 2007 U20 World Cup held in Canada.