That extra-time touch of class provided the Ports with safe passage past the first hurdle on the path towards this weekend’s final.
Casement’s personal Irish Cup adventure has featured highs and lows but the full-back is hoping to close the story of the season in style at The Oval with a winner’s medal.
The set-piece specialist added the crucial second goal in a 2-1 fifth-round defeat of PSNI and the first, a penalty kick, to help defeat Linfield during the quarter-final tie.
Injury and suspension, respectively, forced him out of dates against Portstewart and Ballymena United. A decision by the Irish Football Association Appeals Committee last Friday cleared Casement of a six-game ban for an alleged headbutt against Dungannon Swifts in the Danske Bank Premiership.
Portadown’s case included substantial verbal and video evidence - including a statement by the alleged victim, Terry Fitzpatrick, confirming Casement’s innocence.
Now the full-back - who has walked off the pitch in each Irish Cup appearance this season with a spot on the scoresheet - will switch his focus back to football following weeks of off-field issues.
“It is a massive relief and I am delighted everything has now been put to bed,” said Casement, following news of last week’s successful appeal. “It has taken a lot longer than we wanted or thought.
“It had been weighing me down, plus it did annoy me the fact that so much focus was on me and this situation, other than the team, as we moved closer to the Irish Cup final.
“Thankfully, now I can turn to training to try and get my place in the Irish Cup final side.
“All along I was a million per cent certain of my innocence.
“However, when the first hearing went against me I was gutted.
“I cannot thank Terry Fitzpatrick enough for stepping forward and doing what he did, especially as he is a guy I had never previously had a conversation with, so it proves he is a top professional and a gentleman.
“I also owe my thanks to everyone connected to Portadown Football Club for backing me 100 percent.”
The drama connected to Casement’s cup campaign has led to some sections of the Portadown support backing the defender to grab the spotlight on Saturday.
However, Casement is adopting a more pragmatic viewpoint.
“I do not really go in for omens or anything and it is more important to do everything right we can this week with our preparations,” he said. “You need to go in with the right mindset and training plays a big part in getting that side of it all correct.
“Some say things are written in the stars but my view is we must work hard and approach the match with our normal game.
“You cannot play the occasion, only the game, so it is vital we handle the pressure.
“We must get the basics right and go in with the right temperament.
“Having been to three finals with Linfield in a short space of time, it is easy to get caught up in the adrenalin buzz then the next minute it is the final whistle.
“We have experience but, more importantly, a real hunger in the squad.”
Casement’s practical approach is also applied to his set-piece success, the latter a growing part of the team’s attacking threat.
“Statistics show how high the percentage is now of goals coming from corners or free-kicks,” said Casement. “It is something we are encouraged to do as full-backs and I put a lot of practice into my deliveries.
“However, first and foremost I am a defender and want that clean sheet.”