O'Neill said: "Reading have done very well. Brian McDermott has stepped in there as manager and revitalised them.
"I think the game itself will be very difficult, as every bit as difficult, if not more, than against Crystal Palace in the last round. You saw how difficult that tie was for us.
"But, if ever there was an incentive to get back to Wembley again, last Sunday should be it. There was disappointment at the time and it is exactly the same feeling today."