Following a slow start to the campaign, the defending Great Eastern-YEO's S.League champions headed into Sunday's match level on points with their unfancied opponents, but things looked promising for the hosts after Hougang's Azhar Sairudin received his marching orders midway through the first half.
However, Tampines failed to make their numerical advantage count and shockingly went a goal behind on the stroke of halftime when Mamadou Diallo opened the scoring for the Cheetahs.
Rovers then spent much of the second period banging on the Hougang door but were met with stubborn resistance, until captain Aleksandar Duric finally found the breakthrough in the third minute of injury time, salvaging a point for his side.
Elsewhere, Home United moved to the top of the table after recording a 4-2 win over Albirex Niigata.
The Protectors went behind in the fourth minute to Sho Kamimura's well-taken strike, but hit back through goals from Frederic Mendy and Shotaro Ihata.
Qiu Li added another from the spot for Home, and while Kamimura pulled one back immediately, Mendy then added his second to secure the win for his side.
In Sunday's other game, Harimau Muda returned to winning ways with a 3-1 win over Courts Young Lions at the Yishun Stadium.
Jonathan Toto put the Young Lions ahead after 16 minutes, but his strike was cancelled out by Harimau playmaker Nazmi Faiz four minutes after the restart.
From then on, there was only ever going to be one winner, and Ong Kim Swee's charges went on to claim all three points courtesy of a Ahmad Hazwan Bakri strike, and another from Nazmi.
Saturday's only game saw Gombak United and Woodlands Wellington play out a 0-0 draw.
On Friday, Geylang United brought high-flying Balestier Khalsa back down to earth with a 3-1 win, while SAFFC condemned Tanjong Pagar United to a 3-1 defeat.
The week's action kicked off on Thursday with DPMM FC holding Harimau Muda to a 1-1 draw in a hot-tempered clash.
Sunday's S.League Results
Tampines Rovers 1-1 Hougang United
Harimau Muda 3-1 Courts Young Lions
Saturday's S.League Results
Friday's S.League Results
Thursday's S.League Results