Vote for NXT, get a stranger: Weatherill

South Australians who vote for Nick Xenophon will end up picking someone they've never even heard of, the state's premier has warned.

Jay Weatherill says the independent MP is a populist and taps into anger of blue collar workers fearful for their futures and jobs.

"Nick's great - everyone loves Nick, but you might accidentally get someone that you're not expecting," he told ABC radio on Thursday.