Going into the 84th minute the contest was goalless and both sides had a full complement of players.
It finished 10 vs 10 with a goal at either end, the equaliser from Coventry scored in the eighth minute of stoppage-time.
Daniel Johnson’s penalty which put North End in front had come in the 89th minute and there the controversy really started.
The spot kick was a straight forward decision for referee Keith Stroud, home substitute Fankaty Dabo bundling Emil Riis to the floor.
As the last man, Dabo was shown the red card – a fate also bestowed on Liam Lindsay a minute or so earlier for his second yellow card of the day.
From the award of the penalty to Johnson taking it, there was a gap of three minutes due to two Coventry fans coming on the pitch.
The first was tackled by stewards and led away but as he was being whisked off, on came a second.
After his loop of the grass, he escaped back into the stand but his identity is out there for all to see.
If their actions were in some way designed to put DJ off his penalty-taking duties, they didn’t work.
However, the delay was factored into the time added on by Mr Stroud.
Six minutes was put on the fourth official’s board and yes, we know that is the minimum.
More than seven had been played when Fabio Tavares netted a fine finish for the home side’s equaliser.
How much of added-on time was for the two fans running on, only Mr Stroud will know that.
But North End were left with a sense of frustration and perhaps injustice that the delay caused by the pitch incursions ultimately counted against them.
A PNE fan ended up on the pitch too after Johnson had scored – he was quickly removed – so it wasn’t all one way.
Supporters coming on to the pitch is creeping into the game and it needs to stop.
There was the incident in the FA Cup tie between Nottingham Forest and Leicester when a Leicester fan ran on and threw punches at celebrating Forest players.
That lad is now doing four months inside.
There was the incident at Rotherham vs Accrington game when a fan emerged from behind the goal to kick the ball off the spot as an Accy player prepared to take a penalty.
Taking the emotion of the finale out of it, in the cold light of day North End had done enough to win the game.
For the opening 25 minutes they played second fiddle to Coventry but without too many scares in their penalty box.
Ryan Lowe’s men then got on top and created three or four good chances which could have taken them into the lead. Going down to 10 men was the spur they used to go upfield and win the penalty which really should have won them the game.
A number of times PNE have been the comeback kings this season with late equalisers and winners.
This time the boot was on the other foot as Coventry delivered the late blow to earn themselves a point.
That equaliser caused a bit of a needle between the two benches, resulting in Lowe and Coventry’s assistant manager Adi Viveash shown a yellow card each.
Let just say the two sets of coaching staff won’t be on one another’s Christmas card lists in the future.
Referee Stroud was busy with his cards all afternoon, yellow and red.
Two Coventry players and four from North End were shown yellow, the second waved at Lindsay followed by a red card.
The Scotsman committed three fouls all afternoon and was punished for two of them.
His first caution came in the 17th minute for a block on Martyn Waghorn which Lindsay could have little complaint about.
The second was more of a coming together between him and Vikto Gyokeres rather than anything cynical.
Gyokeres fell into the advertising hoardings which probably made it look worse than it was. But North End hearts sank when Mr Stroud went for his side pocket for yellow and then fished out the red card.
Winding the clock back from there, the better chances had come PNE’s way.
City keeper Simon Moore saved twice from workhorse Ched Evans in the first half.
Early in the second, Evans met a Cameron Archer cross and headed against the foot of the post, Moore swiping the loose ball away with his foot as Evans moved in to meet the rebound.
With 11 men on the pitch Lowe had outlined his attacking intent with the first substitution he made.
Off went Josh Earl to be replaced by Riis, with Daniel Johnson switched to the left wing-back slot. Riis joined Evans up front with Archer dropping into the hole behind.
They could have shut up shop when Lindsay went for his early shower but within a minute or so, Johnson led a charge up the pitch and played in the overlapping Riis who was felled by Dabo who had been caught out by his pace.
Johnson was the calmest man inside the ground as others lost their heads, sending Moore the wrong way with his spot kick.
Bambo Diaby came on to restore a three-man defence at that point, with Ryan Ledson replacing Evans as the clock ran down.
Coventry had one last push, Gyokeres fouled by Andrew Hughes who had lost his footing.
The free-kick into the box came off two Preston heads and out towards the left.
Tavare got on the ball, moved inside on to his right foot and curled shot into the far corner over Daniel Iversen.
It felt like a defeat as the home side celebrated, the tension between the benches spilling over.
PNE left with a point but really it should have been all three – a missed opportunity.