He also joined with his fellow swimmers Květoslav Svoboda, Josef Horký, and Martin Škacha in the men's 4 × 200 m freestyle relay.

Swimming the lead-off leg, Rubacek recorded a split of 1:51.37, and the Czech team went on to finish heat two in seventh place and thirtieth overall, for a total time of 7:26.26.

[4][5] At the 2008 Summer Olympics in Beijing, Rubacek qualified for the second time in the men's 100 m butterfly, by clearing a FINA B-cut of 53.71 from the European Championships in Eindhoven, Netherlands.

[6][7] He challenged seven other swimmers in the fourth heat, including three-time Olympians Ioan Gherghel of Romania and Juan Veloz of Mexico.

[8] At the 2009 FINA World Championships in Rome, Italy, Rubacek dipped under a 52-second barrier, and lowered his record to 51.99 seconds in the preliminary heats of the 100 m butterfly.