Born in Sydney, New South Wales, Klemmer played his junior football for All Saints Toongabbie before being signed by the Parramatta Eels.
At just 15 years of age, Klemmer signed with the Canterbury-Bankstown Bulldogs.
David played for the Bulldogs' NYC team in 2011 and 2012, scoring 6 tries in 28 games and sending worrying signs to every other team who witnessed his damaging size.
At the end of 2012, Klemmer was named at starting prop in the 2012 NYC “Team of the Year”. He was also named NYC “Player of the Year”.
Often seen charging down the field with three or four defenders hanging off him, Klemmer impressed the Canterbury coaching staff.
Klemmer was described as the Glenn Lazurus of his day, weighing in at 120kg with the ability to play 80 minutes of football.
Peter Mulholland, who worked with the Bulldogs to recruit Klemmer, told the Daily Telegraph “He was wearing a size 18 shoe when he was 15.”
Klemmer made his NRL Debut in Round 1 of the 2013 season against the North Queensland Cowboys and appeared in four matches for the Bulldogs starting off the bench.
Klemmer missed the back end of 2013 due to a serious knee injury but has successfully recovered and will be back to play a big part in the Bulldogs 2014 NRL campaign.