Wales will have to play a friendly before their first Euro 2020 qualifier against Slovakia in March 2019, with Germany among the potential opponents.
Wales have been drawn in Group E with Croatia, Slovakia, Hungary and Azerbaijan.
Because there are only five in the group, each team will be without a game on two of Uefa’s 10 matchdays.
According to Euro 2020 competition regulations, every team with a free matchday must fill it with a friendly.
There will be four potential European opponents for Wales on each of their blank matchdays, though it is also a possibility they could face non-European opposition.
Wales, who host Slovakia on Sunday, 24 March 2019, do not have a qualifier scheduled on the first matchday (21-23 March 2019) or the sixth matchday (8-10 September 2019).
Manager Ryan Giggs and the Football Association of Wales will discuss potential opponents, with Germany, Denmark, Kosovo and Serbia all free on the first matchday in March.
On the sixth matchday in September, the other teams without a qualifier will be Bulgaria, Ukraine, Belarus and the Republic of Ireland. Wales host Azerbaijan on Friday, 6 September.
Group E second seeds Wales are likely to favour a home friendly in March, as they would like to avoid travelling before their important opening qualifier at home to third seeds Slovakia.
Uefa, European football’s governing body, implemented the same rule for the first Nations League campaign, which ended in November with Denmark topping Wales’ group.
On the occasions Wales did not have a competitive fixture, they played friendly matches against Spain in October and Albania in November, losing both.
Wales v Slovakia, Sunday 24 March (14:00)
Croatia v Wales, Saturday 8 June (14:00)
Hungary v Wales, Tuesday 11 June (19:45)
Wales v Azerbaijan, Friday 6 September (19:45)
Slovakia v Wales, Thursday 10 October (19:45)
Wales v Croatia, Sunday 13 October (19:45)
Azerbaijan v Wales, Saturday 16 November (17:00)
Wales v Hungary, Tuesday 19 November (19:45)
Full Euro 2020 qualifiers draw
Group A: England, Czech Republic, Bulgaria, Montenegro, Kosovo.
Group B: Portugal, Ukraine, Serbia, Lithuania, Luxembourg.
Group C: Netherlands, Germany, Northern Ireland, Estonia, Belarus.
Group D: Switzerland, Denmark, Republic of Ireland, Georgia, Gibraltar.
Group E: Croatia, Wales, Slovakia, Hungary, Azerbaijan.
Group F: Spain, Sweden, Norway, Romania, Faroe Islands, Malta.
Group G: Poland, Austria, Israel, Slovenia, Macedonia, Latvia.
Group H: France, Iceland, Turkey, Albania, Moldova, Andorra.
Group I: Belgium, Russia, Scotland, Cyprus, Kazakhstan, San Marino.
Group J: Italy, Bosnia-Herzegovina, Finland, Greece, Armenia, Liechtenstein.