The Aston Villa manager was critical of the state of the playing surface at the national stadium during the 2-1 defeat to Manchester United in the Carling Cup final, claiming there "was no excuse" for the poor conditions.
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The pitch may have been relaid before the semi-finals following the concerns raised about it.
O'Neill said: "It's great to be back at Wembley again - even on that pitch.
"I didn't enjoy the occasion at all last week so there is a chance to put that right now.
"It took us time today before we treated it like a quarter-final in the FA Cup.
"You need character and determination to fight and we didn't have that in the first half.
"But it came back in great abundance.
"It's fantastic for the football club to be in the semi-finals and I genuinely feel for the supporters. They were fantastic.
"Even at 2-0 down to a Championship club they were cheering us on and that was a big boost."
Villa were staring at an upset when Shane Long's two goals put the Royals in control at the break but from the moment Ashley Young pulled one back within two minutes of the restart the Premier League side moved through the gears.
Carew scored twice in the space of six minutes to put Villa ahead before the hour mark before capping the win with a penalty in stoppage-time.
Villa's run to the Carling Cup final saw an even more thrilling game when Blackburn were beaten 6-4 in the semi-final, and O'Neill conceded that his side had produced some dramatic football in the cups this season.
He said: "There have been some great games this season and that is what cup football is about.
"We go for it and so have other teams against us. Reading's part shouldn't be underplayed.
"They were fantastic and played it like a quarter-final from the first whistle. They were terrific."