Olejniczak played his first professional tournament in 2002 on the third-rate ITF Future Tour . Two years later he won his first single and double title there. In 2005 he achieved a series of 17 wins in doubles on the Future Tour, which brought him four more titles. In August he made his debut on the ATP World Tour in Sopot . He received a wild card from the tournament officials for the doubles, where he lost with Maciej Dilaj against the third seeded Argentinians Lucas Arnold Ker and Sebastián Prieto . He finished the year in the top 350 in both singles and doubles.
In 2006 he won his first title on the ATP Challenger Tour . After not getting past the quarter-finals before, he won his first final in San Luis Potosí alongside Daniel Garza . By reaching the final in León , he improved by over 100 places in doubles and in July was 206th, his best place in the world rankings . Olejniczak made his Davis Cup debut for Poland against Nigeria . He won his two individual games and contributed to the 5-0 success of his team. He was used in three singles matches in his career and has a score of 3-2.
In 2008 he achieved his only single title win on the Challenger Tour. In Mexico City he defeated the top seeded American Sam Warburg in the final . After he failed to qualify at the Australian Open and French Open , he survived them for the first time at Wimbledon and was in a Grand Slam main draw . There he had to admit defeat in three sets to the top 30 player Gilles Simon in the first round . In August he reached his career high in singles with 185th place. In doubles, Olejniczak won two more titles in Aarhus and Stettin and stayed in the top 300.
In March 2009 he won his last title on the Challenger Tour in Sarajevo . Subsequently, he did not survive a quarter-finals in either singles or doubles, which slipped in the world rankings. On the Future Tour he won two doubles and one singles title, but he finished 2010 in singles in 468th place and in doubles in 786th place. He made his last solo appearance in 2012 in the qualification of Poznan , and ended his career two years later after losing a semi-final at a futures tournament in Italy.
Poland
Mexico city
Sam Warburg
Raphael Durek
Aarhus
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Jean-Julien Rojer
David Marrero
Sarajevo
Konstantin Kravchuk
James Auckland Rogier Wassen