Career
Club
Born in Poland, he moved to France with his family at the age of three. His father Bernard is a former professional Polish football player and his mother Renata a former handball player. He made his Ligue 2 debut in October 2008, coming on as a 25th-minute substitute against LB Châteauroux.
In July 2009 he joined Arka Gdynia on a one-year loan with a buy option.
His season ended in March as a result of injury. Despite wishing to retain him, the small club did not take up the buy option due to cost.
In February 2011, he joined Arka Gdynia on two and a half year contract. International
Siebert was a part of the Poland U-21 team