Rafa Benitez felt Matt Ritchie's disallowed goal should have stood at St Andrew's.
Championship leaders Newcastle United were held to a goalless draw by Birmingham City this afternoon.
Benitez's side had the better chances, and Ritchie had a strike disallowed late in the first half by referee Simon Hooper.
The winger felt he was level with Ayoze Perez, whose initial shot was saved by Tomasz Kuszczak.
"We have seen this so many times and we are a little bit disappointed," said Benitez, who had been forced to name Jonjo Shelvey on the bench after the midfielder had been laid low by illness in the build-up to the match.
"I think that we did what we had to do with the problems that we had, but still we did well, we had control of the game and we had some chances.
"We had a goal, and I have seen the replay – disallowed when it should have been a goal.
"We were doing really well. They had a couple of counter-attacks that could have been dangerous for us
"And when they are in a difficult position you can understand why it is hard for them to play in the way they want to play, but we did what we had to do.
"We controlled the game little by little and created chances, but we weren't able to take them because their keeper did well."
Kuszczak also denied Ritchie and Daryl Murphy after the break.
United are a point ahead of second-placed Brighton and Hove Albion, who were beaten 2-0 by Leeds United at Elland Road this evening.
Third-placed Huddersfield Town, beaten 4-0 by Bristol City last night, are seven points behind Newcastle, though David Wagner's side have a game in hand.
Follow NUFC writer Miles Starforth on Twitter here