"I took a bit of time and to be honest I thought Derby wanted me more," he told BBC Radio Derby after talks with both clubs.
"I spoke to Nigel and everything I want as a footballer he was telling me this club wants to do."
Elsewhere, Sheffield United have snapped up Tranmere defender Andy Taylor for an undisclosed fee while Middlesbrough are set to sell Stewart Downing to Aston Villa for £12m.