By Gabriel Tan at the Bishan Stadium
Jozef Kaplan opened the scoring for the Eagles in the sixth minute when his close-range shot was deflected past Nazri Sabri, but after Qiu Li had restored parity from the spot in the 36th minute, the visitors reclaimed the lead four minutes before the break when Khayrulhayat Jumat bundled home after Home failed to deal with a Khairulnizam Jumahat corner.
However, the hosts pulled level again in the 50th minute when Shotaro Ihata powered in a header at the far post, before they edged ahead for the first time five minutes later when Qiu sent a six-yard strike in off the crossbar.
And in a stunning 23-minute surge, Mendy then netted an astonishing four times to put his side 7-2 up, although the visitors finished off the scoring deep into injury-time when Kaplan grabbed his second with a stunning long-range effort.
Home headed into the game fourth on the table and desperately needing a win to get their title hopes back on track, after losing two of their three games in the league since the mid-season break, including a comprehensive 3-0 defeat to SAFFC last Thursday.
And while they would have taken heart pre-game by the fact they beat Geylang 7-1 when the sides met earlier this season, Lee Lim-saeng's men were handed a rude awakening after just six minutes when Mun Seung-man capitalised on a misplaced pass by John Wilkinson and drove into the box, before drilling the ball back across the face of goal for Kaplan to score via a deflection off Nor Azli Yusoff.
14 minutes later, the lively Michael King glided into the box and forced Nazri into a smart save with a fiercely-hit effort, before an excellent cross from the Geylang winger was just beyond the reach of the unmarked Mun, who had been left unmarked five yards out from goal.
Despite being at opposite ends of the table from their title-chasing opponents, the Eagles were completely dominating proceedings and were unlucky not to be in possession of a greater lead.
But nine minutes before halftime, Home were handed a fantastic chance to equalise after Firdaus Idros did well to keep the ball alive down the left and drew a foul from Mubarak Ahamad inside the area. Referee K. Kalimuthu had no hesitation in awarding a penalty, and Qiu duly delivered the goods for his side by sending Yazid Yasin the wrong way.
Nonetheless, the defensive problems that have been plaguing the Protectors all season long came back to haunt them in the 41st minute when they failed to react after a Khairulnizam corner had deflected off the crossbar. Instead, Geylang centre-back Khayrulhayat was first to react and promptly prodded home the loose ball to put his side back in front.
Two minutes later, Ihata, who had been dropped from the Home starting XI for the last three games, forced a fine save from Yazid after cleverly controlling a Firdaus cross on his chest and firing in a half-volley, and then wasted another good chance shortly after when he blazed over from close range after Mendy had flicked the ball into his path.
But there was to be no denying the Japanese striker five minutes after the break when he outjumped his opponent at the far post to meet a perfectly-weighted cross from Qiu, and powered home a header that Yazid failed to keep out despite getting a hand to.
Five minutes later, Geylang shot themselves in the foot when Zul Elhan Fahmi gave away possession to Firdaus inside his own area, allowing the Singapore international to advance on goal before laying the ball back for Qiu to stab home.
By now, the momentum had swung firmly in Home's favour although they were dealt a blow a minute in the 59th minute when Qiu had to be replaced by Indra Sahdan Daud after picking up a knock on his left ankle.
However, his replacement nearly made an instant impact when he broke free down the right and picked out Mendy with an excellent cross, only for the usually-prolific Frenchman to miss from point-blank range.
Seven minutes after the hour mark, Indra again released Mendy with a terrific 40-yard pass in behind the Eagles backline and this time, the Protectors marksman made no mistake lashing a shot into the far corner to give the hosts a two-goal cushion.
12 minutes later, the partnership worked wonders once more as the ex-Singapore international ran half the length of the field after a fast break by Home, before squaring the ball across the face of goal to leave his strike partner with an easy tap-in.
Seven minutes from time, Mendy completed his hat-trick when he leapt highest to meet a Shi Jiayi freekick with a glancing header that crept just inside the far post, and two minutes later, he grabbed a fourth when he beat Yazid with a sublime lob from just inside the area, after Indra had once again carved the Geylang backline open with a visionary pass.
Having seen all their good work in the first half evaporate before their very eyes, the visitors mustered one final effort to restore some pride, and Nazri had to pull off a flying save to keep out a firm header from substitute Danial Razali.
But from the resultant corner, Home could only clear the ball straight to the waiting Kaplan, who sent a looping effort beyond the reach of Nazri and into the back of the net to give his side the smallest of consolations.
Home United: Nazri Sabri, Nor Azli Yusoff, Sofiyan Abdul Hamid, Kenji Arai, Masrezwan Masturi, Firdaus Idros, Shi Jiayi, John Wilkinson (Jeremy Chiang 39'), Qiu Li (Indra Sahdan Daud 59'), Shotaro Ihata, Frederic Mendy.
Geylang United: Yazid Yasin, Khairulnizam Jumahat (Amy Recha Pristifana 69'), Syed Fadhil, Khayrulhayat Jumat, Jalal, Zul Elhan Fahmi (Ang Zhiwei 61'), Mubarak Ahamad (Danial Razali 82'), Jozef Kaplan, Michael King, Mun Seung-man, Stefan Milojevic.