Aberdeen boss Derek McInnes felt a "poor decision" from referee Willie Collum proved pivotal as his side fell to a 2-0 defeat by Hibernian at Easter Road.
Collum awarded Hibs a penalty after Lewis Ferguson caught Jamie Murphy late as the winger sent a cross behind the byline, and Martin Boyle converted in the 27th minute.
Aberdeen struggled to get back in the game with their new-look attacking set-up and Boyle got in behind to double the lead midway through the second half.
McInnes, who lost Greg Leigh to a hamstring injury in the opening moments, said: "There was nothing really in the start of the game, the pitch was difficult for both sets of players, and I thought the penalty decision had a big bearing on how the first half played out. And I think it's a poor decision.
"I like Willie Collum and I think he's one of our best referees, but I just don't see (that's a penalty).
"Murphy does well driving into the box, but he toe-pokes into the side-netting and Lewis has actually tried to stop himself going into him. Having seen it again, it's such a harsh decision.
"I didn't think we responded well to that, Hibs had the ascendancy.
"We tried to make changes to bring (Callum) Hendry and (Niall) McGinn on to get three up front and get more support to Fraser Hornby, but that does leave us a wee bit exposed and Boyle's speed and movement capitalised on that.
"That was probably their only chance second half, but they had the game won at 2-0 and it was up to us. Unfortunately we had loads of effort and got into good areas, and I know we have hit the bar, but our quality of cross wasn't good enough."
The Dons have now not scored in four games and only won once in eight and McInnes can understand the fans' frustrations after they fell five points behind Hibs in fourth place in the Scottish Premiership.
"We have offered up far better than that over the piece," he said. "It's not a stat we are proud of and it's disappointing we are on that type of run but we work hard to try and address that."
Hibs have now won three games in a row and Boyle has been at the heart of their impressive form with four goals.
Hibs head coach Jack Ross said: "He has looked back to his best in recent weeks again.
"He is one who had a little dip, had some personal issues as well. We left him out a few weeks ago and I think he benefited from a little bit of a rest, mentally and physically.
"He has settled a lot now, and bringing Chris Cadden has helped a lot because it has allowed us to free him up to play higher up the pitch and more centrally when we need to. That suited the game and he was bright throughout."
Ross added: "I think we look strong again as a group. A lot of individual players dipped at the same time five or six weeks ago and they are all looking strong again and sharp and bright.
"We had to get back to being better out of possession, we got a bit ragged for a few games. You need that discipline to give you the foundation to win games because we have got an attacking threat and a creativity in our group."
