Brian Smith resigned as Wakefield Trinity Wildcats head coach with immediate effect on Tuesday.
Wildcats captain Danny Kirmond revealed Smith had told the players he had stepped down because of "personal reasons".
The 61-year-old Australian took over from James Webster towards the end of last season on a rolling 12-month deal, but Wakefield have managed just one victory from five league matches so far this season.
The first one was to keep Wakefield in the top-flight with a play-off victory over Bradford last year but he has won just once this season and they are again in the bottom-three.
According to the Daily Star, Smith took training in Featherstone on Tuesday before he travelled to Belle Vue Stadium and "stunned" chairman Mick Carter with the news.
Wakefield have confirmed they will hold a press conference at 12.30pm on Wednesday at their Belle Vue home.
Smith broke the news to the Wakefield players after training on Tuesday morning and Kirmond admitted it came as a bombshell.
"It was a shock for us," Kirmond told the Wakefield Express. "Brian told us that his decision was due to personal reasons and nothing to do with us, as players.
"He didn't go into any detail but we have to respect his decision. This is professional sport and these things happen.
"Brian is a great coach. We learned from him and he did a lot to keep us in Super League last year."
Smith, who had been in the job just nine months, is the second coaching casualty since Super League kicked off just under five weeks ago.
Smith achieved his short-term objective of keeping the Wildcats in the top flight, courtesy of their victory over Bradford in the £1m Match in September, and two months later agreed to stay on for 2016.
Wakefield won just five of their 20 matches under the former Sydney Roosters, Newcastle and Parramatta boss, and he was critical of his players following Sunday's 42-28 home defeat by Catalans Dragons.
Wakefield assistant coaches Stuart Dickens and Lee Gilmour, who stepped into the breach until Smith's arrival last June, are likely to be again placed in temporary charge for the club's next game at St Helens on Friday.
Smith, who turns 62 next Monday, was in charge of his third English club following spells earlier in his career with Hull and Bradford. He is expected to return to Australia, leaving younger brother behind at Warrington.