It's a massive day for both the Republic of Ireland senior and under-21 sides.
First up, Jim Crawford's under-21s have the chance to qualify for a major finals for the very first time.
They take on group leaders Italy in Ascoli, with the winners qualifying automatically for next year's finals in Georgia and Romania.
Ireland are guaranteed a playoff place regardless of today's result, and kick-off is at 4.30.
Senior manager Stephen Kenny will be forced into personnel changes for tonight's Nations League game with Ukraine.
Saturday's hero against Scotland - Michael Obafemi - is out with a groin injury.
Shane Duffy and John Egan are also missing, meaning Blackburn's Darragh Lenihan is set to win a first competitive cap.
Kick-off in the Polish city of Lodz is at 7.45.
And Kenny says it's important to be flexible when it comes to personnel and the style of play
The other game in Ireland's group has a 5pm start in Yerevan, and sees Armenia play Scotland.
Australia booked their place at the World Cup finals last night, with a penalty shootout win over Peru in Qatar.
The last vacant spot in this winter's finals will be filled this evening.
Costa Rica play New Zealand from 7, with the winners landing in Group E with Spain, Japan and Germany.
