Second-placed City were held to a 0-0 draw by Adelaide United at AAMI Park on Saturday night,
Saturday night's draw also means City could yet let second place slip - and with it an Asian Champions League Elite berth and the first week of finals off - while Adelaide's finals hopes are all but over.
A victory at AAMI Park would have kept pressure on Auckland at the top.
Instead, Steve Corica's charges, the first Kiwi side to win the premiership, can celebrate their first silverware when they host Perth Glory at Go Media Stadium on Sunday.
Auckland (50 points) lead City (45), Western Sydney (43), Melbourne Victory (42) and Western United (41).
"I thought we were excellent tonight, really aggressive, dictating the game for long periods," City coach Aurelio Vidmar said.
"Unfortunately you need to score to win the game, and that was the only thing really that was missing from the game.
"Disappointing obviously because a win would have put us in a much better position, so there's a hell of a lot to play for next week."
City host Sydney FC next Saturday.
The scoreless draw on Saturday is a hammer blow to Adelaide's finals hopes because the Reds (sixth, 38 points, -2 goal difference) don't play again and require Sydney FC (seventh, 37 points, +12 goal difference) to lose their next two games.
Outgoing coach Carl Veart has likely led the Reds for the final time, while the match also appeared to be club great Isaias and fellow veteran Javi Lopez's last games.
"Hopefully it's not the end of the season," Veart said.
"But it wasn't one of our normal performances tonight. We didn't look as fluent as we have been.
"But we showed great resilience and we dug in and we kept a clean sheet - we haven't done one of them for a long time.
"Proud of the boys and the way they fought tonight right through the home game, so we'll see.Â
"We've snuck in there at the moment and Sydney have to do something in the next two games."
Talented Reds striker Archie Goodwin, who is joint golden boot leader with Sydney's Adrian Segecic on 13 goals, suffered a right hamstring injury in the first half.
"It doesn't look good, which is unfortunate," Veart said.
"I think he's got a tear in the hamstring - I'd say even if we do live another day this season he won't take any part again this year."
City, whose unbeaten A-League Women team were presented with their premiers plate at halftime, took control in the second half and peppered the goal (17 total shots to six) without reward.
City goalkeeper Patrick Beach brilliantly came off his line to deny Dylan Pierias late.
But City couldn't find a winner, with youngster Lawrence Wong dragging two late chances heartbreakingly off-target.
