Has Oklahoma City uncovered the next hidden gem out of Australia’s NBL? Members of the Thunder staff were spotted in Australia this week for the NBL preseason. The National Basketball League has produced four first round picks in the last three NBA drafts, three being lottery selections. Two of these lottery picks, Josh Giddey and Ousmane Dieng, ended up in Oklahoma City. The Thunder returned to the NBA’s new recruiting grounds this season to take a peek at Rayan Rupert, a member of Dieng’s former team, the New Zealand Breakers. Rupert is the NBL’s next tantalizing young prospect; the 18-year-old…