 Runkauskas played in the Lithuanian Pupils Basketball League (MKL), for the V. Chomičius basketball school.Runkauskas started his professional basketball career in the Klaipėda, NKL (Lithuanian 2nd Division) team, Nafta-Uni-Laivitė, in 2003.After he became a champion of the NKL, in 2007, with Nafta-Uni-Laivitė, Klaipėda's strongest basketball club invited him to join their team.