Wales would face either Finland, Ukraine or Iceland in a home play-off semi-final for Euro 2024, should they fail to qualify automatically.
Win that and they would need to beat either Poland or Estonia in a one-off final to reach next summer's finals.
Rob Page's side can still reach Germany directly if they beat Turkey in Cardiff on Tuesday and Croatia drop points at home to Armenia.
But Wales' Nations League status gives them a play-off place regardless.
Results elsewhere in Europe on Monday night confirmed Wales' semi-final options.
If Wales do enter the play-offs, a Uefa draw on Thursday will decide which of the three they would face in a single leg semi-final in Cardiff on Thursday, 21 March.
The final would be five days later, Tuesday, 26 March, with the hosts also decided by a draw.
Italy's goalless draw with Ukraine and the Czech Republic's 3-0 win against Moldova saw them both seal qualification on Monday night - meaning Poland and either Wales or Croatia would be the only sides from the top group of Nations League sides not to qualify automatically.
With a minimum of four sides needed for each play-off path, teams from lower Nations League tiers make up the numbers.
It would mean the highest ranked League D side Estonia playing best-ranked League A side Poland, and Wales facing one of the best-ranked runners up from League B not already allocated a play-off place.
Two of Finland, Ukraine and Iceland will remain in their own path, with one moved up.
The new format of play-offs are not new for Wales; they qualified for the 2022 World Cup by beating Austria in a home semi-final before overcoming Ukraine in Cardiff.
Ukraine finished third in Group C behind England and Italy. Finland, who beat San Marino 2-1 on Sunday night, finished third in Group H behind Denmark and Slovenia, above Kazakhstan and Northern Ireland.
Iceland finished fourth in Group J with Luxembourg in third behind qualifiers Portugal and Slovakia.
Should Wales beat Turkey and Croatia fail to beat Armenia, Croatia would enter the play-offs as top seeds. They would face Estonia at home, with Poland hosting one of the League B sides.
Wales captain Ben Davies said the side have not given up hope of qualifying automatically for what would be their fourth major finals from the last five.
Manager Page revealed he has told the squad to not consider the play-offs while the possibility of finishing in the top two remains a possibility.