QPR visit Wigan for the first leg of their Championship play-off semi-final on Friday after falling short in the race for automatic promotion.
Redknapp's men finished 13 points below second-placed Burnley and now face a stern examination if the London club are to be successful in their quest to seal an immediate return to the Premier League.
"Wigan will be a tough game - they're a very good side," said Redknapp.
"Being at home in the second leg is important for us, but our only focus at the minute is on preparing for Friday at their place.
"I think there are four very evenly-matched teams in the play-offs.
"Everyone will head into them confident of promotion, but we'll just have to wait and see what happens.
"This league is so unpredictable, and I don't see the play-offs being any different. It's all up for grabs for us - we're going to give it a right go."
A last-gasp 2-1 win at Nottingham Forest and Reading's 2-2 draw with Burnley secured sixth spot for Oscar Garcia's men, who were eliminated at the same stage 12 months ago by eventual play-off winners Crystal Palace.
But the south-coast club are widely regarded as the underdogs and will need to be wary of a Derby team experienced a record-breaking season under Steve McClaren.
Derby completed the double over Brighton this term as McClaren's men set a new club points record, totalling 85 from their 46 games.
"We have done nothing yet. Now we want to finish the job off in the play-offs and that's our next aim," McClaren told The Derby Telegraph.
"We have to make sure we continue to do what we have done over the last 46 league games.
"We have to remain focused, defend well and play football because that is what has got us into this position.
"This is no time to change what we've been doing."
