Preston North End boss Alex Neil felt Sheffield United's penalty which dumped his side out of the FA Cup at Bramall Lane was 'contentious'.
Tom Clarke's challenge on Billy Sharp in the 80th minute saw referee Graham Scott point to the spot, Sharp getting up to score the penalty for the contest's only goal.
Neil said: "I'm disappointed, you don't want to lose any game.
"I didn't think there was much in the game at all, the statistics suggest that - chances for, chances against are relatively similar.
"I thought we just shaded the first half and Sheffield United were probably better in the second half.
"The disappointing thing was that we went out to a contentious penalty, having watched it back about six times it is still a wee bit inconclusive for me - I'm not 100% sure it was a penalty.
"Leading up to it, there was a free-kick given against Jordan Hugill on the half-way line, I spoke to the fourth official right after it and he was telling the referee 'good challenge'.
"That is frustrating and then the actual penalty decision itself, with the referee's positioning it is real difficult for him to tell whether Tom plays the player first or the ball first.
"The referee was behind it and I thought the linesman was probably in the best position to make that decision and he didn't get involved in it."
Neil did admit that Clarke needed to be more careful in the position he was in and felt the tackle didn't have to be made with Sharp going away from goal.
"Tom didn't need to make the challenge, I have discussed that with him," said Neil.
"It was probably a bit of a rash decision from Tom in that area of the pitch but equally I'm not convinced it was a penalty either."
Overall the fourth round tie was a disappointing, both sides having made a number of changes with one eye on league games on Tuesday.
Neil made eight changes and Blades manager Chris Wilder seven.
"I thought we played relatively well without really creating much and I think they would probably say the same," said Neil.
"There weren't a huge amount of chances created in either box, I think we had six shots and they had five, they had two on target and we had one.
"That suggested there wasn't a lot in the game."