Wellington Phoenix's 1-1 draw against Adelaide United last weekend handed Sydney a record fourth title for finishing top in the regular season, but this defeat left it with just one win in its past five matches.
This was Melbourne's first match since the restart yet it showed no sign of rust and it required a string of first-half saves from Andrew Redmayne to keep it goalless at the interval.
Craig Noone and Jamie Maclaren found the net in the second half to give second-placed Melbourne a boost in its bid to claim a first-round bye.
Noone made the breakthrough in the 57th minute, taking advantage of a mishap between Paulo Retre and Redmayne to pass into an empty net.
Maclaren made sure of the three points when capitalising on more hesitancy in the Sydney defence – this time from Ryan McGowan – to score his competition-leading 19th A-League goal of the season.