Danny Blind said he would think about whether he should continue as Netherlands coach after his side lost 2-0 to Bulgaria on Saturday.
After finishing third at the 2014 World Cup under Louis van Gaal, the Dutch missed out on Euro 2016 and now find themselves in fourth place midway through their campaign to reach Russia, six points off the lead in Group A and three back of a potential playoff spot.
Spas Delev scored twice in the opening 20 minutes and Blind's side could not find a response, leading the manager to consider his future, though he was not ready to immediately resign.
"I blame myself," he told national broadcaster NOS. "It can't go on like this. Things have to change."
Asked about his future, he said: "I need to think about it. I do not throw the towel in here. I'm incredibly disappointed, especially since I had a good feeling about this match.
"It makes sense that I put myself in front of the mirror."
Blind conceded before kickoff he was taking a risk starting Matthijs De Ligt who, at 17, became the youngest Netherlands debutant since Mauk Weber in 1931. But the coach said injuries to other centre-backs forced him to select a player with only a handful of appearances for Ajax.
De Ligt's dream debut quickly turned into a nightmare as the teenager was immediately on the back foot and failed to stop Delev on both goals.
"Of course, it's easy now to judge it was maybe too early" for De Ligt to start, Blind said.
Despite calling the defeat a "nightmare," Netherlands captain Arjen Robben stuck by both De Ligt and his coach, saying the players "are on the pitch and we have to perform."
"There was a lot wrong," Robben said. "We can point fingers but that does not make sense.
"That does not change the result. We lost here, and those are the hard facts. If we play a good game, we win here. But we did not play a good game, or even a bad game. This was a terrible day."