Norwich City manager Alex Neil criticised the decision not to award his team a first-half penalty in the 1-0 Premier League defeat at Chelsea on Saturday.
Willian appeared to bundle Robbie Brady to the ground shortly after the half-hour mark, but referee Craig Pawson opted not to point to the spot.
Diego Costa went on to settle the match in the 64th minute as Chelsea leapfrogged Norwich into 15th.
"It's a key moment for both teams," said Neil. "Quite a lot this season we've not really been getting decisions our way.
"I think there's been a disallowed goal, a few penalty decisions that were blatant penalties that we haven't got and I thought we should have had the penalty on the half-hour.
"I don't ever say anything about referees because I think they've got a hard enough job but it gets extremely frustrating. When you are one of the smaller clubs, it just becomes really difficult to accept.
"Their little minor decisions mean a great deal to us because we might not have five or six glaring opportunities where we can score, so when you do feel as if you deserve a penalty, you would like it to be awarded."
Costa's goal came as a result of Cesc Fabregas' quick thinking from a free-kick.
"We gave the foul away, the first thing we should do is either get round the ball to stop it being taken quickly or take the ball with us," added Neil. "We can switch on quicker, recover our positions quicker, and we didn't.
"That lapse in concentration ultimately cost us the match. Once that first goal comes in, it's then tough because we've then got to change our mindset and be more aggressive.
"But you've got to remember the boys have got 70 minutes of hard work in their legs and what you don't want to do is try to be too expansive and turn a good, solid, steady performance for a 1-0 into maybe three or four."