The midfielder produced a crucial clearance from Sean Murray's goalbound strike that his namesake, Hollywood Kung Fu star, Jackie Chan would've been proud of in the second half as Derry held a precarious 2-1 lead.
"It was one each at the time and a few of the lads were talking about it there and they reckon my reaction after my clearance off the line was better than my goal celebration," he laughed. "It's as good as a goal and I'm as happy with that as I am with the goal."
Admittedly the Creggan man had played his part in Dundalk's opener as he lost possession before Murray brushed off the challenge of Darren Cole and fired past Nathan Gartside 33 minutes into the final match of the league campaign.
He certainly made amends, however, with a rare strike from distance which gave Derry hope of a comeback on the stroke of half-time.
That spectacular goal inspired a second half display which ultimately clinched fourth position in the league table, as Jamie McGonigle's eighth goal of the season spoiled the party for Dundalk at Oriel Park.
Derry had to better Bohemians' result against Sligo Rovers and while Harkin claims the players were deliberately kept in the dark as to how events were unfolding at the Showgrounds, he knew it was always going to be a nervous finale to the 2021 campaign with so much at stake.
"It was a nervous feeling coming down," he admitted. "There was a lot at stake and we tried to have the mentality that we had nothing to lose but we knew in our bellies that it would be tough and it would be down to us to make sure we got the win otherwise we wouldn't be in with a chance. We got there in the end. What a game and what a night.
"We didn't know what Dundalk we would be playing against but we knew there's good players there and they were good on the night.
"We didn't start well and it was my own fault giving away the ball for the first goal," he confessed. "I didn't have a great first half. I probably wasn't even in a position to shoot for the goal but I just thought 'I'll have a go' because it couldn't have gotten any worse in the first half for me and it just happened to go in the net. It's my first (league) goal all year and I'm buzzing with it.
"I scored against Drogheda in the Cup but I have a new role this year and haven't had many opportunities to score. It's been playing on my mind all year but I just accepted that I'm not a goalscorer and there's other people in the team who can do that.
"The timing of the goal, just before half-time gave us something to play for coming out for the second half and we got there in the end.
"I'm glad I recovered from giving the first goal away and glad we got the win in the end."
They certainly did thanks to that clearance and of course McGonigle's clinical finish into the bottom corner of the net seven minutes after the interval.
"We know how good a finisher Jamie is and it just happened to fall perfectly. It was like it all happened in slow motion. I took a look and thought 'ah it's Jamie' so I was just expecting it to go into the net and thankfully it did."
Former Derry City striker Georgie Kelly scored an equaliser for Bohs in Sligo to set up a mouthwatering finale to the season but as it stands the Gypsies must win the FAI Cup next week if they're to take European football away from Harkin and his teammates.
"Obviously Bohs were playing when we were playing but I didn't know it was Georgie who came on to score but when you have boys like him coming off the bench you've always got a chance to score goals. We had one job tonight and knew if we got a win we would have a chance. Thankfully it went our way.
"Hopefully it goes our way in the cup next week. If it doesn't we can do nothing about it. We got ourselves in the position. We had a bad run at the start of the season but now have a chance to be playing in Europe next year, so it's been a great season."
'Jackie' emerged from the Derry dressing room after the game to celebrate with the large travelling Derry support which included his fiance Demi and his daughter, Indie.
It was a special moment for the midfielder who had become disillusioned last season after his self-confessed worst year in football where he saw limited game-time.
It's been a remarkable transformation since as he's relished in his new, more disciplined role in the heart of the Derry midfield. So what does he put the turnaround in fortunes down to?
"It's just down to belief and having that confidence," he stated. "We got those wins after the first six games and it was just about pushing on from there. It's great belief in what we are as a squad and we believed in how good the players are in there. We know how good we are and we showed it at times this year. It makes everyone excited for next year. It's not up to us next week but hopefully we get to Europe.
"Getting 'Fats' (Patrick McEleney) and Mickey Duffy back is brilliant and hopefully Ruaidhri can get a few more players to boost the squad and he's kept a lot from what we have this year. What we have already is strong and it's only going to get stronger."