Zalewski played college hockey for four years at Clarkson University, scoring 108 points in 151 games.

Following a brief stint with the Worcester Sharks of the American Hockey League at the end of the 2007–08 season, Zalewski played 75 games for the team in 2008–09.

After scoring a goal in three games at the beginning of the 2009–10 AHL season, Zalewski made his NHL debut with the San Jose Sharks on October 12, 2009 against the Phoenix Coyotes.

[3] After two seasons in Finland, Zalewski continued his career abroad, moving to Germany in signing an initial one-year deal with the Straubing Tigers of the DEL on June 17, 2015, that was extended for another year in 2016.

[4] He featured in international hockey for the first time in 2015, playing three games for the US National team in the Deutschland Cup in Germany.