Castelen's brilliant hat-trick fired the Wanderers to a pulsating 5-4 win over Brisbane Roar at their home stadium on Sunday and into the A-League's championship decider against Adelaide United.
The Wanderers' comeback win, having fallen behind 3-0 after the opening 23 minutes, has been hailed as one of the 11-year league's greatest games and 32-year-old Castelen was thrilled to have played a decisive role.
"I scored some hat-tricks in under-21s for Holland ... but on this stage the game was massive for our club, for the players, for everyone," the Suriname-born Dutchman told reporters.
"Even for me to be involved, to score a hat-trick at the highest level at this moment, it’s a great step to the main goal, to win the final. It was a great moment to take in but the job is not done yet."
Among the most prolific shot-makers in the A-League but with a conversion rate of only four goals coming into the semi-final, Castelen fired over the bar early in the Roar match to elicit groans from Wanderers fans.
The team promptly slumped to a 3-0 deficit but Castelen rallied them with a thunderous free kick from outside the box that cleared the Roar wall and veered into the left-hand corner of the net.
His second, swooping on a defensive deflection before hammering the ball off the cross-bar into the net, levelled the match at 3-3 before he put his team in front with a low-range strike.
Jamie McLaren scored his second for Roar in the 81st minute to give the Brisbane team hope, but Australia forward Dario Vidosic had the final say in extra time.
Former Feyenoord winger Castelen earned the last of his 10 caps for Netherlands in 2007, with his career hitting a cross-roads after a number of injury-plagued seasons with Hamburg.
He came to Sydney after a brief stint in Russia and a second spell in his home country and has now become a favourite among Wanderers fans, renowned as the country's most vociferous football fans.
In the Wanderers' last game at Pirtek stadium before its redevelopment, the terraces were jumping and Castelen marvelled at the atmosphere.
"They are massive," he said of the Wanderers fans, many of whom will travel to Adelaide Oval for Sunday's final, the team's third after two runnerup finishes.
"For Australian football, from Western Sydney, this is amazing ... I have people calling me from Europe saying the game was unbelievable.
"It’s not only the fans, it’s the quality of the game ... People were in tears. That shows the club and the fan-base we have."
(Reporting by Ian Ransom; Editing by Amlan Chakraborty)
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