Danny Wilson couldn't hide his disappointment at the 'mental block' that saw the Blades exit the Johnstone's Paint Trophy on Tuesday night.
After a 1-1 draw at Coventry City after 90 minutes, David McAllister cancelling out a Harry Maguire own goal, Maguire and Ryan Flynn then missed from the spot and with the Sky Blues successful converting theirs, United slipped to a 4-1 shootout defeat.
Speaking afterwards, the Gaffer said: "I am disappointed in the manner of the defeat; we seem to get a mental block when it comes to a penalty shootout.
"The second half performance was very encouraging, though, and we take heart from being able to give of the young lads the experience of playing against a strong Coventry side.
"After our goal we perhaps had the momentum to go and snatch the game but, to be fair, there wasn't a great deal between the two sides.
"We are disappointed to be eliminated; of course we are, because I thought this was a real opportunity to progress further. Saying that our priority remains the league, but aside from the FA Cup we can now solely focus on that.
"We knew this would be a real test for us, but at the same time we had confidence in the lads coming into our side.
"Both teams cancelled each other out for much of the game and chances were certainly at a premium. The goal we conceded was very unfortunate to say the least, it gave them a lift but we made a couple of changes and that brightened us up, going forward."
Commenting on the shootout, Wilson concluded: "As the game neared the end our supporters were probably dreading penalties. I thought we would break the hoodoo but again we haven't kept our composure.
"Getting over this problem comes purely with practice; we just wish the lads would replicate what they do in training when it comes to a shootout."