Melbourne Victory's trip to Korea to face Ulsan Hyundai on April 4 became all the more important after Tuesday night's 1-0 win over Kawasaki Frontale.
Victory's win, and Ulsan's 1-0 defeat to Shanghai SIPG, means both sides are level on 5 points heading into Match Day 5.
In the AFC Champions League, head-to-head record is the first 'tie-breaker' should teams finish level on points in the Group Stage.
That means a win for either club will secure their qualification through to the knockout stages (Round of 16) of the tournament - with a game still to play on Match Day 6.
In the event of a draw on Match Day 5, and if both sides finish level on points after Match Day 6, the next relevant criteria will be away goals followed by goal difference.
If Victory and Ulsan are level on points at the end of the Group Stage:
A 1-1 or 2-2 draw on Match Day 5 would see Ulsan Hyundai through on away goals.
A 3-3 draw would require goal difference to seperate the clubs.
A 4-4 draw (or higher) would see Victory through on away goals.
Group F standings
WATCH: Kosta's late winner against Kawasaki