The 39-year-old Del Piero, whose two-year contract expires at the end of the season, set up both his team's goals at Sydney Football Stadium in the final match of the regular season to put the Sky Blues into an elimination playoff at Melbourne Victory next week.
The evergreen Italian laid off a cross that 20-year-old midfielder Terry Antonis hammered into the net from outside the box in the 38th minute.
Though Rostyn Griffiths equalised for Glory on the stroke of halftime, Del Piero deftly lofted a pass into the area that team mate Richard Garcia ran onto and duly struck home three minutes into injury time.
Melbourne Victory thumped New Zealand strugglers Wellington Phoenix 4-1 away on Saturday to finish fourth in the regular season standings and among the top six sides that contest the playoffs in the tradition of Australian sport.
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Defending champions Central Coast Mariners will contest the other elimination playoff next week against Adelaide United who limped into the postseason with a 2-0 loss away to Newcastle Jets.
Hosting the clash in their east coast base in Gosford, the Mariners will be brimful of confidence after upsetting the high-flying Brisbane Roar 2-0 at their Lang Park fortress on Saturday.
The two-times champions Brisbane had booked their playoffs ticket weeks ago, however, and still finished the regular season a yawning 10 points ahead of second-placed Western Sydney Wanderers.
As the top two sides, both Roar and the Wanderers earn a week off to prepare for semi-finals against the winners of the first week's elimination playoffs.
Wanderers, the last year's runners-up, overhauled lowly Melbourne Heart 3-2 away on Saturday, raining on retiring captain Harry Kewell's valedictory match in front of 10,000 fans.
(Reporting by Ian Ransom; Editing by Sudipto Ganguly)
