The Championship campaign has been quite the white-knuckle ride for Sheffield United and Nottingham Forest, whose stressed-out fans must now contend with the anguish of being put through the playoff wringer. The idea of promotion to the top flight was extremely fanciful for both clubs in the early months of the season, with bad starts prompting concerns that they were more likely to go down than up. But after their playoff semi-final that starts on Saturday at Bramall Lane, one of these storied clubs will be a Wembley showpiece away from football’s fabled “dreamland”.