The sharp fall in the British pound against the U.S. dollar that rattled markets earlier Friday is a worrying sign for the sterling, says Sean Callow, a senior currency strategist at Westpac Banking in Sydney. "This is a price move you would expect from an emerging-market currency, not from the third most-heavily traded pair in the world," says Callow. He says the move is reminiscent of a flash crash in April 2013 that sent the gold price down by about $200 in just moments. The metal price never fully rebounded, signaling a similar scenario might transpire for the pound. "It's not going to recover, there's no bottom, just air below," he says.