Wellington sit in second place with three games remaining.
His go-ahead penalty was his 39th goal for the German club this season and 15th against Arsenal in his career.
The rivals are the last two teams to win the European club trophy.
The NZ women had beaten their rivals 4-0 three days earlier.
The Merseyside club have dropped further down the ladder.
The midfielder is hanging up her boots after a 166-game career at senior level.
Chris Wood has now found the back of the net in four consecutive matches.
Liverpool move back to second but have a game in hand.
The result moved the Mariners ahead of the Phoenix at the top of the table.
The Phoenix were pipped at the post in Gosford.
There was only one team in it in Christchurch on Saturday.
The Phoenix can go a long way towards the premiership title with victory over Central Coast Mariners this weekend.
The Reds leapfrogged Arsenal, who beat Luton Town on Thursday (NZ time).
Their status maybe short-lived, with Liverpool scheduled to play overnight.
The All Whites captain has found the back of the net for the third straight game.
Alex Rufer was red carded late in Sunday's win over Brisbane Roar.
The Reds are now two points clear atop the standings after their win over Brighton.
The skipper will miss next week's top-of-the-table showdown with Central Coast.
The NZ captain missed last week's international window through injury.
The Wellington side finished their 22 games with nine wins and a draw.
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