Curtis (from Blackburn Rovers) gifted Nottingham Forest and David Johnson a goal in the Semi-Final 2nd leg when he couldn't properly defend a Reds attack.
United face Wolves in the final at the Millennium Stadium, £25,000,000 is at stake.
The game will be his last for the Blades as his loan spell ends but it is said that Neil Warnock will attempt to sign the former Manchester United player if 'Mission Cardiff' is successful.
"From a personal point of view, I was just so hugely relieved that the lads got me out of jail," said Curtis.
"The final now promises to be a brilliant occasion and already we can't wait. Wolves will be difficult opponents and there is no way that we'll be taking anything for granted."