Van der Vaart missed Saturday's 2-1 win over Sunderland with a calf strain and with several other midfielders absent Redknapp was desperately hoping the Dutchman would recover.
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Gareth Bale, who scored a hat-trick last time Spurs were in the city, when they lost 4-3 to Inter in the group phase, misses the game with a back injury and Jermaine Jenas is suspended.
Luka Modric is struggling to make the starting side as he recovers from an operation to remove his appendix less than two weeks ago.
After flying to Milan on Monday and having a light session, Redknapp was able to report good news on Van der Vaart.
"Rafa is OK. He had a calf strain but he should be OK," Redknapp told reporters.
BACK INJURY
Bale, who has missed several games with a back injury, did not travel with the squad.
"It's a big loss, he didn't feel great," said Redknapp, who said he did not want to rush the Welshman back too early.
Bale's absence has been somewhat countered by the return to the first team of Niko Kranjcar, who has scored the winning goals in Spurs' last two games.
"Kranjcar is in a great form he showed it last Saturday, he also has international experience. He won't let us down for sure," Redknapp said of the Croatia midfielder.
Having trailed 4-0 to Inter in his last trip to the San Siro before Bale's hat-trick brought respectability, Redknapp said he would not be changing the style that also brought a 3-1 win over the holders at White Hart Lane.
"It is very difficult to change approach. I certainly can't ask players like Aaron Lennon to do defensive job because this his not their nature. They have to play their natural game."
Captain William Gallas said the experience of playing in the San Siro would help his team.
"Harry tells us not to be afraid of any team, we just want to win, and win and win," he said.
Milan boss Massimiliano Allegri said he was expecting that approach to continue.
"I think Tottenham scored the highest number of goals in the group stage, they are very strong in attack," he said.
"But they conceded several goals as well."
Allegri is also struggling with injuries and said he had yet to decide on his lineup or his formation.
"I still have to make a decision on (Alexandre) Pato. We only have three strikers available, it will be different without (Antonio) Cassano," he said.
"It
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