Manager Robert Page says Wales will "throw everything" into the Euro 2024 play-offs after missing out on automatic qualification following a controversial 1-1 draw with Turkey.
Croatia's 1-0 win over Armenia meant Wales could not qualify automatically.
Wales were in contention when they led and the game in Zagreb was goalless.
But referee Matej Jug awarded Turkey a dubious second-half penalty after rejecting three Wales penalty appeals in the first half.
Asked if Wales would have won had there been a different referee, Page said: "I believe so."
He added: "I have to be careful what I say, it was a stonewall penalty against Brennan [Johnson], one of the most obvious I have seen, and we have conceded the softest penalty I have ever seen.
"It's so frustrating at this level. I can't get my head around it. But the performance? I thought the lads were excellent. We were going for the win and everyone could see that."
Wales' penalty appeals were for a challenge on Harry Wilson from Abdulkerim Bardakci and two in quick succession on Johnson from Samet Akaydin.
The last of those was Wales' strongest shout, with Akaydin barging into Johnson's back at a corner, but Slovenian referee Jug somewhat bafflingly chose not to point to the spot.
Stranger still was his decision to award Turkey a penalty after Wales captain Davies barely brushed against Kenan Yildiz, with Yusuf Yazici converting the spot-kick.
The Cardiff City Stadium crowd voiced its anger but even a Wales win would not have been enough.
Wales faced a tall order trying to qualify automatically because they needed to beat Group D winners Turkey while also requiring 2022 World Cup semi-finalists Croatia to drop points at home to Armenia, 85 places below them in the world rankings.
It would have been different had Wales not drawn in Armenia last Saturday. Had they won in Yerevan, victory against Turkey would have secured automatic qualification.
However, Page's side knew they had already guaranteed themselves a place in March's play-offs, thanks to the fact they had been in the top tier of the Nations League's most recent edition.
Wales will host Ukraine, Finland or Iceland in a one-legged play-off semi-final on 21 March.
If they win through that, they will face Poland or Estonia - with home advantage to be decided via a draw this Thursday - in another one-off tie five days later, with the winner securing their place at next summer's tournament in Germany.
"Now we will focus on that. I am off tomorrow [Wednesday] to Switzerland for the draw on Thursday," said Page.
"We will throw everything into that. Our preparations start now for the play-offs. We will know more on Thursday who we have got.
"I'm pleased it's a home draw. What our supporters do is incredible. They help us get the results.
"This place [Cardiff City Stadium] is a fortress. Croatia, now Turkey, you go back to Austria, Ukraine [last year] - we have had some big nights here. The crowd are massive in helping us achieve the wins."