Van der Vaart's fitness is a concern, with the Holland international having struggled to shake off a niggling hamstring complaint.
"He sometimes has a problem with that Rafa," said Redknapp.
"He has had a few hamstrings since he's been with us, but he's important to us - he scores goals. He's an amazing finisher. Last season I think he got 12, this season he's capable of getting near 20 goals from playing in that position where he likes to play."