Huddersfield Town's Aaron Mooy is preparing to host Socceroos teammate Mathew Ryan for the first time when Brighton head north in the Premier League.
The Terriers have slid down to 16th place in the table and since beating Manchester United in October they have scored just twice in six matches.
But a fifth victory at John Smith's Stadium this season would see Town leapfrog Brighton, back in the top flight themselves after automatic promotion and currently two points better off in 12th.
"A must-win game is a final, where you have no chance to correct something and this isn't the case on Saturday," Huddersfield manager David Wagner said.
"But it's a massive game for all of us and a great opportunity in front of our supporters to play Brighton and be in front of them after the game.
"There are so many important stories in this game. This is why it's a big game, but it's not a must-win game because a lot more will follow after this.
"If you had offered me 15 points after 15 games and then Brighton at home, I would say absolutely," he added.
In England's second tier, Bailey Wright's Bristol City can move to outright third in the Championship when they travel to Sheffield United on Friday. Both sides are on 37 points, six and 10 respectively behind Cardiff and leaders Wolves.
James Meredith's Millwall travel to an Aston Villa side still reeling from the latest injury blow to Socceroos captain Mile Jedinak, while Massimo Luongo's QPR have a tough task when they host Leeds on Saturday.
North of the border, Tom Rogic and Celtic will look to make it 68 domestic games unbeaten when the Bhoys travel to Hibernian.
Across the Channel, Mathew Leckie's 12th-placed Hertha Berlin travel to an Augsburg side with their eyes on the Bundesliga's top four. Things are more dire in the 2. Bundesliga for Robbie Kruse's VfL Bochum, who are just above the relegation zone as the Winterpause looms.
Bochum head south to Regensburg on Saturday.
Defender Aziz Behich's year to remember will get even better if his sixth-placed Bursaspor can knock off third-placed Fenerbache in the Turkish Super Lig, while Tomi Juric's FC Luzern face a tough away trip to Zurich.