Nominations for the position will close on Monday, August 19 but already Barrett is being touted as one of the frontrunners for the gig.

Barrett ran for the seat of Orange in the 2016 byelection but lost in a tight race to the Shooters Party in a state seat the Nationals had held for 40 years.

He now works in the DPI in Orange and is a former advisor to ex-Primary Industries Minister Niall Blair. A shearer's son, he was born and raised in Orange.

Bathurst's Sam Farraway, a former candidate in a Federal Nationals Senate preselection, is another among a field of an expected 10 people for the NSW Upper House preselection to be held on September 5.

Mr Farraway is a long-time president of the Bathurst Agricultural, Horticultural and Pastoral Association and is managing director of Hertz, Bathurst and chairman of the Bathurst Nationals branch.

Also in the running is Karen Hogan, from the North Coast. Mrs Hogan is studying a Masters of Advanced Practice Nursing.

She's worked at Lismore Base Hospital for 11 years and is keenly involved in community events. She is the wife of Federal Nationals MP for Page, Kevin Hogan.

Mr Blair announced earlier this year he would be leaving parliament, but confirmed it a week ago.

It followed his decision not to seek a ministry in the new Berejiklian-Barilaro Government after fielding death threats while taking up the fight for the Government over the Murray-Darling situation, particularly following the fish deaths at Menindee Lakes. At the time he said the threats had taken too much of a toll on himself and his family.

"Mr Blair has served the NSW Nationals faithfully as a Branch Member, as a Party Chairman, and then in the NSW Legislative Council where he eventually became the Party's Deputy Leader," a statement from the NSW Nationals director Ross Cadell said.

"He proved a strong and resilient leader in our State Government, and served the people of rural and regional NSW to the best of his ability as the Minister for Primary Industries, Lands and Water and later as Minister for Primary Industries, Regional Water, Trade and Industry.

"One of the great strengths of Mr Blair as a Minister and Member of Parliament was his ability to connect with people wherever he went, winning supporters from across the political spectrum and taking their concerns and needs seriously.

"He always strived to do his best for the whole of the State, and poured his efforts into serving the people of our regions."

The NSW Nationals said nominations for the vacated position would close at 6pm on August 19, and a preselection will be held on September 5.

"It has been an honour to work alongside Mr Blair," Mr Cadell said.