Davis will be hoping Oakley and Smith shine this season

Both arrived on three-year deals - Oakley came on a free transfer, while the fee for Smith was undisclosed.

"Oakley is a tremendous signing for us," Rams boss Billy Davies told the club website.

"He is a great addition and at the age he is (28) we feel his best years are around the corner - hopefully at Derby County Football Club."

Oakley rejected a new deal at Southampton earlier in the summer.

Davies said he was excited about seeing Smith play for the Pride Park side.

"He caused us a lot of problems at Preston and I had first seen him when he was on loan at Leicester," added the Derby boss.

"Ryan in an exciting young player who can get fans off seats with his running ability and hopefully throwing a few good balls into the box."