Outspoken coach Raymond Verheijen on Friday night left his role in the Wales set-up just days before he was due to be part of the managerial team for the Gary Speed Memorial Match against Costa Rica.
The 40-year-old was brought into the national side's backroom staff by late manager Speed and proved a popular figure with senior members of the squad, including captain Aaron Ramsey and Craig Bellamy.
But Verheijen's position has been in doubt since Speed's death in November, prior to which Wales had won four out of five games. And the Dutchman took to Twitter to confirm his exit, and accused the Football Association of Wales of "political and destructive games".
He said: "Earlier today I have informed the FAW I will resign. Have enough of their political & destructive games. Very sad day. Very proud to be part of FIFA's most improved team in 2011. Would like to thank the players and fans for an amazing journey."
Chris Coleman, named as Speed's successor last month, had held talks with Verheijen and Osian Roberts, who also worked under Speed, to see if they could work together going forward and was due to take a background role to the pair for next Wednesday's fixture.
Coleman recently chose to bring in Kit Symons as his assistant manager, and Roberts had said earlier this week he was hopeful that the quartet could prove an effective team as Wales build towards their 2014 World Cup qualifying campaign, which begins with a home fixture against Belgium on September 7.
But no decision had been taken on Verheijen's long-term involvement and the Football Association of Wales confirmed his departure in a statement that read: "The Football Association of Wales (FAW) wishes to announce that it has received the resignation of Raymond Verheijen.
"Raymond was the assistant manager to Gary Speed with the Wales national team.
"The FAW accepts the resignation with regret, as Raymond was due to assist the Wales squad this week with the match against Costa Rica, a game being staged in honour of the Wales manager who tragically left us in November of last year.
"In light of the forthcoming match, and the sensitivities of it, the FAW has no further comment to make at this time. The FAW would like to take the opportunity to thank Raymond for his work over the last 12 months and wishes him well for the future."