Somebody who went on to exceed expectations after his stint at Rotherham would be Keith Kettleborough. An excellent mid-field passer of the ball in the Beckenbauer mold, he really came into his own after he was sold to Sheffield United and helped them get promotion to the First Division/Championship. He was a regular in that fairly successful team in the mid-sixties (highest finish fifth; FA Cup Semi-Finalists) and moved to Newcastle. In the run-up to the 1966 World Cup he was selected as part of Alf Ramsay's initial squad of prospective players but didn't make the cut for the final squad.
He was also a pretty decent cricketer