Career
Janczyk began his career at Sandecja Nowy Sącz. In 2005 he joined Legia Warsaw in the Ekstraklasa. On 12 July 2007 he signed a 5-year contract with CSKA Moscow, having impressed the club"s scout at the 2007 Fédération internationale de football association U-20 World Cup.
His first league goal came on 2 September 2007 to earn a 1–1 tie against Football Club Spartak Moscow.
On 23 October 2007 he made his first appearance in the Union of European Football Associations Champions League, coming on in the 76th minute of the 1–2 loss against Internazionale. As of January 2009, all of his appearances in the Russian league have been off the bench.
In January 2009, he joined KSC Lokeren on loan until the end of the season. In March 2009, the loan was extended until the end of the 2009–2010 season, with CSKA Moscow having the right to recall Janczyk during the winter.
In January 2010, he joined Germinal Beerschot on loan until June 2011 with a buy option.
In November 2010, he and Germinal agreed by mutual consent to end his loan agreement early, the manager having given him no playing time in the 2010-2011 season. With CSKA Moscow"s consent, he began training at Legia Warsaw. In February 2012, he played in a trial game for Irish side Limerick and scored a goal.
He has also represented Poland at the junior level, scoring a hat trick against Belgium at the 2006 Union of European Football Associations U-19 Championship.
At the 2007 Fédération internationale de football association U-20 World Cup, he notched 3 goals in 4 games. Argentina had not lost any goals in the tournament until Janczyk finally scored against them in the second round.
In April 2008 Polish national team coach Leo Beenhakker named Janczyk in a preliminary group of 31 players for Euro 2008. However, Janczyk did not make the cut when the group was reduced to the final squad of 23.
He made his first appearance for the Polish national team during a friendly against Serbia in December 2008.
Legia Warsaw
Polish championship (Ekstraklasa): 2006
PFC CSKA Moscow
Russian Cup: 2008, 2009.