QPR head to Villa Park on the back of a two-game winning run that has revitalised their survival bid.
They were seven points adrift of their rivals at the start of the month but back-to-back wins over Southampton and Sunderland has brought safety within their grasp.
Another victory would leave them just a point behind Villa, who occupy the final safety position, with eight games remaining.
"It is a big game for sure," Redknapp said.
"It's a massive game for both teams. We're both in the relegation battle so it will have an important bearing on the league.
"We have to be ready for the game. It will be a great atmosphere at a good ground, stadium, good club.
"The lads are ready. They are in good fettle."
Villa skipper Ron Vlaar this week described the match as "massive" and while Redknapp agrees, he denied the loser's fate would be sealed.
"Not necessarily. If you can get the win it will make a massive difference to how things look on Sunday when you look at the league table," he said.
"It could take us a point from safety, but we have to take it as it comes tomorrow [Saturday].
"We need a result tomorrow [Saturday] at Villa. It's a big game for us."
QPR have lost just twice in nine games in the Barclays Premier League since the turn of the year - a run that has included a win over Chelsea and home draws against Tottenham and Manchester City.
This month's successive wins have followed to ensure they have now started to make up the lost ground and Redknapp is certain that form is starting to play on the minds of their rivals.
"It's not good when the results come through and the teams around you are winning. We've had that," Redknapp said.
"You want them to lose. It makes a difference to everything.
"I'm sure they're looking and thinking 'oh QPR'.
"I think people wrote us off a few weeks ago. Everybody just said 'they're gone, it's a matter of who goes with them'. We're back in the picture.
"We were almost no-hopers and now we are back in there with half a chance. The pressure is really not on us so much.
"We just have to be ready for each game - up for it. Premier League football is on the line and we desperately want to stay in the Premier League."
Redknapp believes the key to his side's recent revival has been finally finding a way to goal.
QPR scored three goals in a league match for the first time in last weekend's win over Sunderland while January signing Loic Remy has proved an instant hit.
The striker, recalled to the France squad this week, has scored three goals since his arrival and netted in both of the recent wins.
"He's come in and hit the ground running and got three important goals for us," Redknapp said.
"To get back in the French squad is great for the lad. It's good for QPR too.
"If he can keep up his goalscoring ratio between now and the end of the season he'll give us a real chance of staying up.
"If he can get five or six goals that would be fantastic."
Redknapp will take a near full-strength squad to Villa park with key duo Adel Taarabt and Julio Cesar returning to training this week.
Playmaker Taarabt missed last weekend's win with a knock and but is expected to slot back in.
Cesar has been in outstanding form this campaign but he will have to displace Robert Green, who has done well in the Brazilian's brief absence.
Full-back Armand Traore is the only concern and was set to have a calf injury tested at training.