Adelaide United have guaranteed a home knockout match in the AFC Champions League, with a 2-0 win away to Gamba Osaka on Wednesday.

The Reds needed to win or draw and rely on the other group result to go their way, but they did the former as striker Sergio van Dijk scored within five minutes of gracing the field as a second-half substitute - a match-winning decision from coach John Kosmina.

Van Dijk flicked home from the near post of a Daniel Mullen cross in the 65th minute in an expertly timed finish to give Adelaide a deserved lead at the Expo '70 Commemorative Stadium.

The Reds made sure of the result late when substitute Akihiro Sato scored an own-goal from an Adelaide corner in the 87th minute.

They secured top spot in Group E and guaranteed a home Round-of-16 clash in the knockout stages of Asia's premier club tournament.

The game began in entertaining fashion, with Iain Ramsay having a sight on goal in the opening 20 seconds down the left side, only to spray his shot into the side netting.

The first-half, however, was highlighted by a number of goal-line saves, as some sturdy defence at either end saw the score remain at 0-0 at the interval despite both sides looking to attack.

Adelaide defender Nigel Boogaard was the thorn in Gamba's side early when he thwarted Brazilian striker Rafinha with a great block, after the Osaka front man was played through by a delightful ball from Takahiro Futagawa.

Gamba denied Fabian Barbiero on 17 minutes, as his shot from inside the area had beaten goalkeeper Yosuke Fujigaya, but defender Tatsuya Uchida was on hand to clear solidly off the line.

Boogaard was again involved with a clutch clearance just prior to half-time, as he managed to deflect a Gamba cross over his bar from right on the goal-line, in what could easily have deflected into his own net.

The second-half belonged to Adelaide and, once van Dijk came on at the hour-mark, the Reds looked infinitely more dangerous.

The striker's first touch was a clever flick on to almost find strike partner Bruce Djite, but Fujigaya just got out in time to collect.

But van Dijk was more clinical minutes later, as he guided Mullen's cross into the roof of the net, and eased the pressure on Kosmina's men.

Gamba defender Sato then sealed the win for Adelaide, as his accidental towering header left Fujigaya with no chance from the late corner, to seal the Reds' passage to a home knockout final.

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