The Mariners put in an almighty shift on Saturday night, scoring a goal in each half to secure third place and a home elimination final in the A-League.
Jack Clisby continued his strong recent form with a goal in the first half, before Marco Urena sealed the deal in stoppage time after debutant Jing Reec had his shot palmed away in the six-yard box.
Alen Stajcic made a number of changes to the starting side from Tuesday, with Alou Kuol, Lewis Miller and Jaden Casella all into the run on side, and Oli Bozanic was ruled out during warmup with Dan Bouman replacing him.
The rejigged Mariners started strongly, and Alou Kuol had the ball in the net early but it was disallowed for a collision between himself and Ryan Scott that allowed the ball to come free.
Tomislav Uskok tried his luck from range and Mark Birighitti was on hand to tip it on to the post, while Lewis Miller headed just over the bar from a corner down the other end.
But moments later the Mariners were ahead, as the ball fell from a corner and Kye Rowles directed a header towards Clisby. The fullback controlled it expertly with his chest before volleying home to give the Mariners the lead, and it was almost two just before the break as Bouman struck the side netting after a break.
There was a big stoppage early in the second half as Dylan Pierias was felled after a collision with Birighitti, and after a lengthy period of time for treatment Pierias was subbed off, and Birighitti made a huge stop on the line just ahead of the hour mark to keep proceedings level.
Bouman and Casella both had chances on the break as the time was winding down, and a huge defensive stand was needed as Western United began to control the weight of possession.
With eight minutes of time added on due to the Pierias injury and plenty of subs, the Mariners struck on the break five minutes into injury time to seal the result.
Matt Hatch and Stefan Nigro conspired to break down a Western United attack, and Nigro passed Hatch out of the corner and into space. The young winger took off, beat two challenges and then released Marco Urena with a well weighted ball, before the Costa Rican played Reec into space.
Reec’s first time shot was destined for the corner but parried by Scott, only into the path of Urena though who fired home to seal the win and confirm the Mariners’ third spot on the table.
The Mariners will now face Macarthur FC in an Elimination Final next Saturday night at 7pm at Central Coast Stadium.