St Patrick's Athletic had to make do with a point at the Brandywell after a 0-0 draw against Derry City in the SSE Airtricity League Premier Division.
In a fascinating encounter, both teams had the chance to win it, but it was the champions who had cause to feel aggrieved.
The Dubliners were up in arms early on when Ryan McBride barged into the back of Christy Fagan just when it seemed as if he would score a tap in, after Gerard Doherty parried Chris Forrester's shot. But referee Paul McLaughlin was unmoved.
Forrester was Pat's biggest threat throughout as he tested Doherty early in the second half but the ball somehow stayed out of the net.
Derry City may have won it late on when Mark Stewart found Patterson in space, but last season's top scorer blazed over.
And deep in added time, Pat's had goalkeeper Clarke to thanks, as he denied Michael Duffy a certain winning goal after the tricky forward had created space to shoot.
However, as the final whistle went, it was Pat's who were the more threatening throughout and they will have been disappointed to leave the Brandywell without a goal or the points.
Derry City were lucky not to concede a penalty on 13 minutes when Gerard Doherty parried a long-range effort from Chris Forrester straight into the path of Christy Fagan.
The Pat's striker seemed set to fire the visitors into the lead but he was challenged from behind by Ryan McBride and went tumbling. It looked a certain penalty for St Pat's but referee McLaughlin said no penalty, much to the incredulity of the Pat's players and manager Liam Buckley.
Stewart was a spectator for the first 25 minutes but the first time he got a run at the Pat's defence, he almost caused a goal, as he cut inside and sent an effort flying across the penalty area with Patterson and Dean Jarvis both within inches of turning it into the net.
Pat's were attempting to make the most of the wind at their backs and another shot from distance, this time from Forrester, saw Doherty parry the ball into the six-yard box again, but Fagan was once more denied a tap in as Cliff Byrne threw himself bravely in the way of the his shot.
Pat's continued to knock on the door in the second half and Doherty was again called into action on the hour mark. The Derry goalkeeper was forced to parry from Forrester and the rebound came straight back to the Pat's man, who was denied a goal when a red and white shirt got a crucial block to send the ball behind for a corner.
Killian Brennan then dinked a tempting cross into a packed penalty area after Derry conceded a free-kick in a dangerous position but Sean Hoare headed over from close range.
The opening that Derry had been waiting for all game finally came with just ten minutes to go and it was an incredible chance for Patterson. Barry Molloy's long range pass was misjudged by Ian Bermingham and Stewart profited, racing down the right before pulling the ball back across the penalty area for Patterson, who somehow blazed it over the bar when it seemed easier to score.
Derry may have won it in added time when Michael Duffy created a shooting opportunity but Clarke denied him with a wonderful save.