Smith signed for Derby on a three-year deal

Smith, released by the Black Cats, becomes Derby boss George Burley's third signing of the close season.

Burley told the club's official website: "Tommy is 24 and has a lot of unfulfilled potential. We now have real competition for places up front.

"We are delighted to have got him, especially as Sunderland made him another offer. He is lightning quick, has good ability and is very sharp."