Ajax Amsterdam manager Ronald Koeman has quit, the Dutch champions said on Friday.
Koeman's departure came after Ajax were knocked out of the UEFA Cup on Thursday after a 3-1 loss to AJ Auxerre. Ajax are in third place in the Dutch first division, eight points behind league leaders PSV Eindhoven.
Ajax said in a statement that assistant trainers Ruud Krol and Tonny Bruins Slot would run the team while the club looked for a replacement.
Koeman said Thursday's defeat had been the last straw.
"Yesterday's result decided it for me. I can no longer summon up the strength and the energy to get over this and to make the team perform better," he said in the statement.
"If I am not completely motivated and driven, I cannot and should not stay as trainer at Ajax. After three years and three months, our successful collaboration comes to an end," he said after a meeting with the Ajax board.
Ajax director Arie van Eijden said he regretted Koeman's decision but accepted it.
"Ajaxis naturally disappointed with how this season has gone. Yesterday's disappointing performance didn't have any direct consequences for us. We have also achieved many successes together with Ronald Koeman," he said.
Pressure has been mounting on Koeman, in his second spell as Ajax coach, after he clashed last year with technical director Louis van Gaal following Champions League defeats by Juventus and Bayern Munich. Van Gaal resigned last October.
Koeman arrived from Vitesse Arnhem in December 2001 to succeed sacked coach Co Adriaanse and won the double in his first season.
He also led Ajax to the league title in 2004 and to the UEFA Cup quarter-finals in the 2002-2003 season.
Krol and Bruins Slot will run the team for the next two matches, Roda JC Kerkrade on Sunday and ADO Den Haag in the Dutch Cup quarter-final on Wednesday, to give the club time to decide about the rest of the season.
Danny Blind, head of Ajax's youth teams, is a candidate to take over but sources close to the club board say Barcelona's assistant coach Henk ten Cate and Tottenham Hotspur manager Martin Jol are also in the frame.