As Sunderland walked off the pitch at Bramall Lane, beaten but unbowed, and applauded by the travelling fans, the step up to the Championship was thrown into stark relief. The margin for error in the second tier is vanishingly small.
A red card, a defender switching off at a set-piece, a bad refereeing decision, an unlucky deflection, a moment of inspiration from an opponent, a goalkeeper lumbering forward to score a one-in-a-thousand header, these are the type of key moments that can tip the balance at any level. But whereas in League One, where Sunderland have spent the last four seasons, you might get away with it, in the Championship better teams and better players will take full advantage.
That is not to say Sunderland will always be on the receiving end - far from it - but they were on this occasion. Alex Neil said before the game that Sheffield United, a side that spent two of the last three seasons in the Premier League, that finished in the play-offs last term, and is again one of the favourites for promotion, would be Sunderland's most difficult test to date.
