Van der Vaart had missed the previous three games with a hamstring injury, but returned with devastating effect to score a brace in a 2-1 victory at Villa that lifts Spurs up to fifth in the Barclays Premier League.
Redknapp, though, had considered hauling off Van der Vaart before his 10th goal of the season due to fears over collecting another injury, and he said: "I took a gamble with him because he has had a hamstring problem, and when he gets tired he tends to get injuries."
He added: "He went to the World Cup and played bit parts all the time and probably didn't get a proper pre-season under his belt.
"So when he gets a bit fatigued he does tend to do a hamstring or something else, and that's what I was scared of.
"I probably left him on for 10 minutes longer than I was going to because when he got hold of the ball at least he would keep it.
"But he has been fantastic for us. He's a 15- to 20-goal-a-year man, and he has everything as a player. He's not just a goalscorer, but a fantastic footballer."
Villa manager Gerard Houllier has revealed Van der Vaart, who also scored both goals in a 2-1 win over the midlands club at White Hart Lane in October, is a player he has twice previously attempted to sign.
"When I was at Liverpool I tried, but he was too expensive, and again when I was at Lyon," said Houllier. "So of course when he sees me, when we meet, it's very funny. We nearly hug each other.
"But it's twice now he has scored two goals against us. He is a fantastic player because he can play different positions up front. What he likes is to play off the striker, but he is disciplined enough to play on the right, the left, everywhere. He makes a difference to their team."
Source: PA
Source: PA