The Wellington Phoenix marked their 100th A-League match in style with a historic triumph at Adelaide United tonight which places them on the verge of successive playoff appearances.

A precious 1-0 victory - just their second in 14 attempts during a campaign marred by woeful results outside of Westpac Stadium - solidifies them in sixth spot with two matches remaining.

They improve to 38 points and have a game in hand over seventh placed Melbourne Heart, who started losing ground with a 1-1 stalemate with the Central Coast last night.

Newcastle, in eighth on 31 points, must beat Sydney FC tomorrow to stay in touch.

The Phoenix stay in Australia for Wednesday's clash with Sydney before rounding out the regular season against lowly North Queensland on Sunday.

After accruing just five points from a possible 39 in their previous trans-Tasman excursions tonight's win - which also broke a five-game duck at Hindmarsh Stadium -- was perfectly timed against an opponent visibly struggling after a three-match schedule in seven days.

The loss was costly for Adelaide, who are no longer able to finish in second place to runaway leaders Brisbane Roar.

English striker Chris Greenacre, one of two changes from the side that beat Newcastle 1-0 in Wellington last Sunday, delivered the decisive blow when his diving header gave Eugene Galekovic no chance in the 34th minute.

While Greenacre's finish was top class the delivery was immaculate from 19-year-old revelation Marco Rojas whose curling right foot cross dissected two defenders.

Rojas, who has laid on five goals in his breakthrough season, was a constant menace and almost laid on a second for Greenacre when he skirted down the by-line, eluding new Adelaide defender Dario Bodrusic, before nudging the ball to the striker who could only direct it straight to Galekovic's midriff.

Greenacre's seventh of the season was also Phoenix's first goal on Australian soil in three matches since the 1-1 draw in at North Queensland on December 27.

Galekovic's counterpart Danny Vukovic was also busy during an entertaining first half, the Perth Glory-bound custodian made his most telling intervention a minute before the break when he advanced to narrow the angle before smothering Paul Reid's strike.

The midfielder, freed to play when the red card he received against the Gold Coast United was overturned by the competition's match review committee, was Adelaide's most threatening attacking force and was on the verge of putting the competition's top scorer Sergio van Dijk through on goal in the 15th minute until Troy Hearfield intervened.

After being dominated for most of the opening half the Phoenix addressed the imbalance but were unable to add a stress-relieving second goal though a long range scorcher from Nick Ward forced Galekovic to tip over the bar in the 49th minute.

Tim Brown also had Galekovic scrambling to his left to palm aside another goal bound strike from outside the area that passed through the legs of Greenacre.

The Phoenix endured anxious moments particularly in the 67th minute when Travis Dodd's right foot shot went between the on-rushing's Vukovic's legs but a desperate lunge from Jade North - restored to the starting line-up after Australia's Asian Cup campaign - clipped the ball on to the crossbar.

Van Dijk was well contained until the dying stages when he spurned a gilt-edged opportunity in the 83rd minute when he a rasping drive flew past the right hand upright while his cross across the face of goal three minutes later was too quick for replacement midfielder Andwele Slory to get a toe on.

Adelaide's defensive structure was disrupted when Brazilian import Cassio retired with a leg injury in the 31st minute while Bodrusic was spared any further torment by Rojas when he was dragged at halftime for Adam Hughes.

The Phoenix lost Vince Lia with a hamstring strain before the half hour mark and was replaced by Daniel who, with starting defender Tony Lochhead were the only survivors from the club's first match in season 2007-08.

A late handball by Andrew Durante meant the Phoenix captain picked up his eighth booking of the season and he will now be suspended for the final two matches of the regular season.

It will force the Phoenix, already shorn of defenders Ben Sigmund and Manny Muscat through suspension, into a defensive rejig for the match against Sydney.

Wellington Phoenix 1 (Chris Greenacre 34)
Adelaide United 0
Halftime: 1-0