The powerhouse clubs clash at the Millennium Stadium with a place in next month's final at Twickenham up for grabs.
Wasps half-back Reddan said: "Wasps and Leicester are the most successful teams in England by a long way, and that is where our rivalry stems from.
"Between them, the two clubs have dominated silverware over the last 10 years. The other clubs between them haven't won the same amount.
"We are successful teams who often end up meeting on the big stage. Past results, when one of us has been thumped, shows the quality and mental strength of the teams.
"Saturday will be a great game and a big occasion. A lot of players have come back from international rugby, and now it's time for us to repay Wasps' understanding for letting us play for our countries."