By Gabriel Tan at the Choa Chu Kang Stadium
Japanese winger Tatsuro Inui netted the only goal of the game in the 35th minute from the spot, after the Warriors were controversially awarded a penalty for handball by Nurullah Hussein.
Despite enjoying the better chances in the second half, Gombak were unable to find a way past an inspired Shahril Jantan, and will now have plenty to do in Saturday's return leg if they are to continue their impressive run in the competition.
Entering the game high in confidence after last Sunday's 2-1 win over Harimau Muda in the Great Eastern-YEO's S.League, the Bulls started the brighter of the two sides, although it was the hosts that recorded the first shot on goal when Zulfadli Zainal Abidin let fly from 40 yards with a terrific strike that Zaiful Nizam had to tip over in the sixth minute.
Young striker Ahmad Suhaimi, who was impressive at the weekend, then left Marin Vidosevic for dead in the tenth minute with a sharp turn near the halfway line before racing down the right, but he failed to make the most of the opening with a poor pass in search of Julien Durand that Shahril easily gathered.
Four minutes later, Bulls captain Obadin Aikhena tried his luck with a 30-yard freekick and although it wasn't the best of hits, the ball took a wicked deflection off the SAFFC wall and nearly crept in at the far post, with Shahril completely wrong-footed by the diversion.
But despite the visitors' lively start, it was the Warriors who eventually opened the scoring five minutes after the half-hour mark, although it came in dubious fashion after a high ball landed inside the area and appeared to bounce back up against the hand of Nurullah.
Referee K. Kalimuthu however immediately pointed to the spot, allowing Inui to step forward and break the deadlock with a clinical effort into the bottom corner.
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Right on the stroke of halftime, Gombak had a good chance to equalise when Hafiz Rahim floated a speculative cross into the box from the right, which Mustaqim Manzur latched onto and burst past two defenders, before sending the ball towards goal. However, Shahril was equal to the task and produced a smart save to push his former team-mate's shot wide.
A minute after the hour mark, SAFFC midfielder Shukor Zailan, who has scored his fair share of crackers already this season, nearly doubled his side's lead when he received the ball 25 yards out and unleashed a piledriver that forced a good save from Zaiful Nizam.
Nonetheless, that was the last time the hosts really threatened their opponents' goal, as Gombak began to pile on the pressure in search of an equaliser.
Mustaqim, who was starting to cause plenty of problems down the wing, whipped in a good delivery into the box in the 74th minute that was met with a powerful header by substitute Jung Hee-bong, only to see Shahril push it away with a fantastic reflex save.
Four minutes later, the veteran goalkeeper came to his side's rescue again when he made a flying save to keep out a 20-yard freekick from Mustaqim, which had looked destined to sail into the top corner.
As the clock ticked over into injury-time, the Bulls had one final chance to level the scores when SAFFC conceded another foul on the edge of the area, but this time, Mustaqim failed to keep his shot on target, leaving coach K. Balagumaran wondering how his side had failed to lose a match they had dominated.
SAFFC: Shahril Jantan, Noh Rahman, Daniel Bennett, Marin Vidosevic, Zulfadli Zainal Abidin, Aliff Shafaein, Shimpei Sakurada, Shukor Zailan (Ruzaini Zainal 81'), Tatsuro Inui, Fazrul Nawaz (Erwan Gunawan 72'), Mislav Karoglan.
Gombak United: Zaiful Nizam, Ismail Yunos, Obadin Aikhena, Walid Lounis, Nurullah Hussein, Hafiz Rahim (Jung Hee-bong 46'), Zulfadhli Emran, Christopher Anderson, Mustaqim Manzur, Ahmad Suhaimi (Samuel Benjamin 89'), Julien Durand.