''It was a great goal, I have to be fair,'' Van Persie said after his stunning equalizer started the Netherlands' 5-1 rout of the World Cup's defending champion on Friday.
''Considering the circumstances, it must be the goal of my career.''
It was also a historic one. By taking his tally to 45 goals for his country, the Manchester United forward also became the first Dutch player to score in three consecutive World Cups.
His special strike started with a pinpoint 40-yard pass from defender Daley Blind. Van Persie flung himself forward to meet it, sending his header sailing over a helpless Casillas, who could only watch as the ball flew into the back of the net.
''I saw Casillas standing a bit in front of the goal, so I decided to go for a loop,'' Van Persie said. ''It just could not have been more perfect. These kinds of goals are scored once in a lifetime.''
The goal was up there with great Dutch goals of the past, such as Marco van Basten's angled volley in the 1988 European Championship final against the Soviet Union and Dennis Bergkamp's spectacular strike against Argentina at the 1998 World Cup in France.
With just a minute to go before halftime, the timing of Van Persie's goal could not have been better. Moments earlier, David Silva had missed a great opportunity to make it 2-0 to Spain when his attempted chip in a one-on-one was blocked by Dutch goalkeeper Jasper Cillessen.
Instead, Van Persie's goal showed once again that teams who squander chances get punished.
And what a punishment it was.
''We scored our goal at the perfect time, at the end of the first half,'' Van Persie said. ''We also scored the second at the right time ... it could have been six or seven the way we played.''
Spain coach Vicente del Bosque made an honest assessment of the striker's performance and the rest of the Dutch side.
''Van Persie tore our defense apart,'' he said. ''They hammered us.''