Huddersfield have sacked boss Simon Grayson, just eight months after he led them back into the Championship after a decade in the lower divisions.
Grayson, 43, has been dismissed after a run of 12 league games without a win left Town 18th in the division and fearing relegation back to League One.
Chairman Dean Hoyle said a return of six points from the last 36 made the former Blackpool and Leeds manager's position "untenable".
Grayson was appointed Lee Clark's successor in February 2012 and won his third promotion from League One three months later when Huddersfield beat Sheffield United on penalties in the play-off final.
His team made a fine start to the season and were in second place in the Championship after seven games before a winter slump culminated in Saturday's 4-0 defeat to Watford.
Huddersfield said in a statement: "Everyone at the club wishes to reiterate and underline our thanks for what Simon achieved in his time here."
Hoyle added: "We brought Simon in with the immediate aim to lead the club to promotion and he did that at the first attempt. It is an achievement for which we are grateful. We knew the transition to Championship football would be difficult and our targets for this season have been realistic, with retention of our status the priority.
"However, having worked so hard to get back into the second tier we have to do everything we can to consolidate that position. After exceeding all our expectations in the early part of the season, our results and performances as a team and from individual players have tailed off alarmingly.
"Worsening displays have accompanied a run of just six points and no wins from the last 12 League games, including some very heavy defeats, culminating at Watford last Saturday.
"Whilst we would all have hoped for even some modest signs of improvement to begin to emerge as the weeks have passed that has not been the case. This has made the position untenable."
Academy manager Mark Lillis and coach Steve Eyre are in caretaker charge for Town, who face Grayson's former club Leicester in the FA Cup on Saturday.