A tight game was turned on its head in the second half when Kingfishers’ keeper Travis Wood saw red and the hosts were reduced to 10 men.
Outfielder Mitchell Palmer had to go between the sticks to face the resultant penalty, converted by the league’s top scorer Chris Ham for 2-0, before Goytre pushed forward to blast another three goals.
The Penperlleni outfit have been the top performing team in the league to date, but having been docked 15 points for fielding an ‘ineligible’ youth team player on the bench back in January, started Saturday’s match one place behind the Kingfishers in sixth.
The visitors should have gone into the lead on 24 minutes when a corner from the left whipped in by left-back Michael Murphy found the head of late arriving centre-half Ross Davies, but his header went wide of the right-hand post.
But in the 33rd minute, Goytre striker Lamin Conteh was played through into the box and his shot was ‘blocked’ by a Monmouth defender’s hand according to referee Huw Marfell, who pointed to the spot.
Kingfishers players and fans voiced their disapproval, but goalkeeper Wood then got himself in hot water with the referee for ‘scuffing up’ the spot, receiving a yellow card.
And from the resulting spot kick, Ham made no mistake, sending Wood the wrong way for his 30th goal of the season.
In the 41st minute Monmouth midfielder Ashley Ford was shown a yellow card for disputing a decision, as tempers frayed, but it stayed 1-0 to the break, with all still to play for.
A foul on Goytre striker Josh Graham in the 62nd minute saw a yellow card for Kingfishers defender Lewis Davies.
And the first round of substitutions came two minutes later when the hosts replaced former Hereford United striker Nick Harrhy with Laurent Ngunjoh and winger Iwan Mooney with Joshua Maksimovic, while the visitors replaced young striker Isaac Wigley with midfielder Joseph Evans.
But it was the Goytre switch which brought immediate results, as Evans put Conteh through into the box who looked to take the ball past keeper Wood, who brought the striker down for penalty number two, resulting in his dismissal.
Monmouth didn’t have a reserve keeper on the bench and had to sacrifice outfield player Palmer to take his place between the sticks, whose first job was to face Ham from the spot.
It was an uneven contest, Ham scoring to make it 2-0 to the visitors with 21 minutes to play.From the restart Goytre managed to wrestle possession in the middle of the park again, Evans playing the ball through to Ham who scored superbly past the stand-in keeper for his hat-trick to make it 3-0.
For the hosts, it now became a battle to try and keep the league’s top scorers at bay for the last 20 minutes of the game, and now adopted an 8/1 formation.
With the game certainly won the visitors made two more changes, youngster Will Higgs coming on for Nathan Gulley on 74 minutes and Abu Sama coming on for Lamin Conteh on 76 minutes.
The hosts made a change on 78 minutes with Lewis Davies replaced by 18-year-old Hywel Williams.
Goytre went into all-out attack mode with all-action midfielder Finn Ryan-Phillips scoring from a great strike from outside the box in the 80th minute for 4-0.
In the 88th minute Monmouth made their final change when they withdrew striker Robert Whitlock and replaced him with 17-year-old Shemar Parkes for the final few minutes.
Then in the second minute of stoppage time, Ryan-Phillips got his second of the game with a tap in from a couple off yards.
The result saw Goytre leapfrog the hosts into fifth with seven games to play.But for the 15-point deduction, Goytre would currently be just one point behind leaders Abergavenny Town - who beat table top rivals Caldicot Town 1-0 at home on Saturday thanks to a JJ Ogogua strike – with four games in hand.
Elsewhere, Chepstow Town beat basement boys Rhayader Town 2-1 at home thanks to a 13th-minute strike from Ashton Ajibola-Gleed and a late effort from Jordan Chappelle.
Monmouth Town’s 2nd XI, with an average age of just 17, fought bravely at FAW Cymru South-East Reserves League leaders Undy Athletic before losing out 3-1.
Monmouth Town travel to face Tredegar Town this Saturday (April 9), before a tough derby away evening clash with Abergavenny three days later.
This Saturday’s (April 9) fixtures also include – Chepstow Town v Aberbargoed Buds, Abertillery Bluebirds v Caldicot Town, Trethomas Bluebirds v Goytre, Monmouth Town 2nds v Newport City 2nds, Abergavenny Town 2nds v Pontypridd Town 2nds, Abertillery Excelsiors 2nds v Goytre 2nds, Caldicot Town 2nds v Tredegar Town 2nds.