Brian Smith has resigned as head coach of Super League club Wakefield Trinity Wildcats.
BBC Radio Leeds reports that Smith asked for his contract to be terminated after speaking to the Wakefield players on Tuesday morning.
Wakefield have won just one of their five league matches so far this season.
Assistant coach Stuart Dickens is expected to take charge of Friday's match at St Helens.
The Wildcats conceded eight tries at home to Catalan Dragons on Saturday, as they suffered a 42-28 loss, with Smith admitting his side needed "to be better".
His spell with Wakefield was his fourth job in England having previously been in charge at Hull (1988-1990) and Bradford Bulls (1996), as well as working as an assistant at national side level.
He also coached at Illawarra Steelers, St George Dragons, Parramatta Eels, Newcastle Knights, and Sydney Roosters in the National Rugby League (NRL).
Wakefield are currently 10th in the Super League table, having only secured their status for 2016 by beating Bradford in the Million Pound Game in October.
The club have declined further comment until a news conference on Wednesday.
BBC Radio Leeds' rugby league producer James Deighton:
"Early season sackings aren't really a surprise these days, but a resignation after just five games of the new season has taken a lot of people by surprise, including myself.
"Brian Smith's arrival at Wakefield was a real coup, and his departure has made headlines too - for a time his name was trending on Twitter within the UK.
"His record in charge reads six wins in 21 games - but tellingly only two of those victories have come against Super League opposition.
"Smith will always be remembered as the coach that saved their Super League status as he guided them to victory in the Million Pound Game.
"However, there will be those who argue that real success would have been avoiding that particular fixture altogether."