Thennis played for the Laredo Broncos of the United League in 2010. Last season, he batted .283 with 62 hits, 10 homeruns, 39 RBIs and 45 runs in 69 games.
A 2008 draft pick of the Chicago White Sox, Thennis played two seasons with Great Falls in the Pioneer League (Rookie). In his first season with the Voyagers, he batted .221 with 42 hits, four homeruns and 21 RBIs in 2008. In 2009, he appeared in 11 games and netted three hits, one homerun and two RBIs.
The Cirrus, Calif., native played two years of college baseball with Texas Tech. As a senior in 2008, he batted .283 with seven homeruns, 60 hits and 42 RBIs. In 2007, Thennis batted .322 with 59 hits, seven home runs and 41 RBIs.
Thennis played one season of baseball at Sacramento City College, where he hit .238 with four doubles and two homeruns in 2006. In 2005, he played his freshman year at American River College, earning Second-Team All-Conference honors and batting .381 with 11 doubles, three triples and three homeruns.