Bishop Auckland manager Brian Honour quit immediately after his team's 3-1 home defeat by Wakefield-Emley, saying: "I can't take the club any further."
Bishops have won just twice in league and cup this season, and Honour said: "Two wins so far this season isn't good enough, but this is a very difficult job.
"There are all sorts of other things to contend with.
"For example, a Northern League Second Division club recently offered a better deal than I could for a player, while I was also hoping to be in the new ground by now.
"But on the other hand, I can take pride from the fact that I helped to save the club from relegation two seasons ago, and took them to promotion last season."
Bishops' chairman Terry Jackson said: "We didn't want him to go. Brian has changed things around quite dramatically, and there was no pressure on him."
Bishops got off to a bad start when Wright scored, and things got worse when they went 2-0 down on half-time.
Mark Foster pulled a goal back for Bishops, but they were finished off when Muller got the third after 75 minutes.
Spennymoor, who have also suffered managerial problems this season with Tony Lee in dispute with owner Benny Mottram, picked up a good point in a 1-1 draw at Bamber Bridge.
Danny Mills scored after 44 minutes for Bamber Bridge, but Tommy Raw levelled from a right wing cross after 63 minutes.
Blyth, under new manager Harry Dunn, lost 1-0 at home to Leek Town.
Whitby had a good 3-2 win at Marine, although they led 3-0 at one stage.
Scott Nicholson, Anthony Ormerod and David McTiernan scored for Whitby.
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