Career
His regular position is flanker or lock. Youth and Varsity Cup rugby
He was included in the Free State U21 squad for the 2011 Under-21 Provincial Championship, but didn"t make any appearances for them. In 2012, he was included in the UFS Shimlas squad for the 2012 Varsity Cup.
He played seven times for Shimlas, scoring tries in their matches against TUT Vikings and Northwestern University Pukke.
He returned to make two substitute appearances during the 2013 Varsity Cup and started in five matches for Shimlas during the 2014 Varsity Cup. Free State
After his first season of Varsity Cup rugby, he was included in the Free State XV squad for the 2012 Vodacom Cup.
He made his first class debut when he played off the bench in their match against the Sharks XV in Bloemfontein. A week later, he started their next match against the Eastern Province Kings in Portuguese Elizabeth, but that turned out to be his only two appearances for the Bloemfontein-based side.
Griffons
Three more appearances off the bench followed before Koster started the final two matches of the season, both of those against the Pumas – first a 39–29 victory for the Griffons in the final match of the regular season and then in the semi-final, where the Griffons lost 37–30.
Koster started five matches for the Griffons during the 2013 Vodacom Cup competition and returned for the 2014 Vodacom Cup competition, where he made three appearances. The Griffons finished third in the competition to remain in the First Division in 2014. He started their semi-final match against the SWD Eagles, where the Griffons ran out 45–43 winners and was once again in the starting line-up for the final against the Falcons.
