Wellington Phoenix saw their Premiers' Plate hopes ended by a 1-1 draw at home to Adelaide United on Saturday.
Sydney FC cannot now be caught at the top of the regular-season standings after a late missed penalty from Ulises Davila proved costly.
Kristian Opseth powered home a header on the hour mark to put the visitors ahead at Bankwest Stadium, but Jaushua Sotirio levelled five minutes later.
Adelaide keeper Paul Izzo made three fine saves to keep Wellington at bay, although arguably the most comfortable of those was from Davila's tame penalty with three minutes to go.
The result means Wellington are 11 points behind Sydney, having played a game more, while Adelaide remain in the top six despite Western United's 2-1 win at Melbourne Victory.
A fine half-volley from Tomislav Uskok and a powerful strike from the excellent Max Burgess put United ahead, with a looping, glancing header from Storm Roux proving scant consolation.