Gary Thornton has left Doncaster RLFC by mutual consent after the club's disappointing start to the season.
The Dons currently sit seventh in Kingstone Press League 1, having lost two and drawn one of the last three games.
General manager Carl Hall said: “I’d like to thank Gary for his efforts, despite results not always going our way he has been a great professional and worked his socks off for us.
“Everyone at the club wishes Gary well for the future.
"Our season aims and objectives remain exactly the same.”
The club were focused on pushing hot favourites Toronto Wolfpack all the way this season and Thornton had been handed a budget to reflect that.
But they already trail the unbeaten Canadian outfit by five points with Barrow also having won all six of their games so far.
Coaches Pete Green, Rhys Lovegrove, Andrew Vincent and Pete Bell will continue to take charge of first-team affairs while the club look for a suitable replacement.
Former York City Knights coach Thornton arrived at the Keepmoat in June 2015, replacing Paul Cooke with the Dons sliding towards relegation from the Championship.
The Dons finished fourth in League 1 last season, losing to Barrow in the promotion play-offs semi-finals.