Career
Gecevičius debuted in the Euroleague during the 2007-2008 season, averaging 3.2 points per game, which he increased to 14.2 points per game in the 2009-2010 season, making him a desirable player in the 2010 summer transfer market. His Euroleague career high is 21 points, scored against Efes. During the 2010-2011 season, he averaged 11.5 points per game in the LKL, and 9.3 points per game in the Baltic Basketball League.
On July 31, 2013 it was announced that Gecevičius will return to Lietuvos rytas.
On July 9, 2015, Gecevičius signed with TED Ankara Kolejliler of the Turkish Basketball League. He also was a candidate to be on the Lithuania national team roster for EuroBasket 2011, and a candidate to be on Lithuanian roster for Eurobasket 2013, however on August 22, 2013 it was announced that Martynas leaves national team due to Jonas Kazlauskas decision.
In 2015 he was included into the extended candidates list, but was not invited to the training camp.
