The Hamburg sporting director was happy to persuade the former Spurs midfielder to return to the club, despite the move representing a change in transfer strategy
Despite being told there would be no money for transfers without player departures, Arnesen proceeded to bring in Van der Vaart and Martin Jiracek in a bid to alter the club’s playing fortunes.
The gamble does not appear to be paying off at this stage of the Bundesliga campaign with the Rothosen currently without a win, having lost their opening two fixtures.
But Arnesen insists it was the right call to make, describing the decision as, "a calculated risk".
"A month ago we had no money to invest. We had a meeting with the board. That’s where we were told: 'Without selling a player we cannot do any transfer for a new player,'" he explained to German newspaper Bild.
"I said three weeks ago that it is better to take a calculated risk. The question was whether we could do that. We could not have bought Van der Vaart without help from outside."
And the 56-year-old was delighted to persuade the Dutchman to make the move from Tottenham to Hamburg on the final day of the transfer window, also claiming he talked to Nicklas Bendtner about a possible switch too.
He added: "I'm thankful that we could get a player like Rafa. That such a player comes to HSV. If you want players of a certain level, they must want to come to Hamburg.
"I have talked a lot to Nicklas Bendtner but he wanted to play European football."