Malaysia Cup holders Kedah and league champions Johor Darul Ta'zim (JDT) kicked off their group stage campaigns with comfortable wins, as Selangor dropped points at home on Tuesday night.
JDT ran out 4-0 winners against Sarawak in Group D, thanks to a Gabriel Guerra brace. Marcos Antonio and Natxo Insa also chipped in goals as the Southern Tigers began their quest to win the only domestic title to have eluded them.
In Group C, Kedah opened their title defence with a 2-0 win over Malaysia Super League (MSL) strugglers Melaka United, with Sandro Da Silva and Baddrol Bakhtiar on the mark.
At Selayang Stadium, Selangor were expected to emerge with three points in a tournament where they have performed so well over the past two seasons.
But MSL promotion hopefuls Terengganu matched them all the way to force a 1-1 draw in Group C's other game.
The game sprang to life in the 25th minute after Selangor's new signing Rufino Segovia did well to make room for himself before curling an effort that was palmed away by Terengganu custodian Suffian Rahman.
Five minutes later, the Red Giants were awarded a controversial penalty after Raimi Mohd Nor was harshly adjudged to have been fouled by Nasrullah Haniff.
But justice was served as Francis Forkey Doe only found the foot of the post from the spot before Segovia blasted the rebound into the side netting.
P. Maniam was forced into a first half reshuffle after A. Namathevan came on for the injured Syahmi Safari in the 43rd minute.
A minute later, Selangor took the lead through Segovia. He drilled home a low effort after taking Doe's pass in stride from a swift counter attack.
Returning veteran Amri Yahyah, deployed in a deep lying position, almost added a second through a long-range free kick. But it was tipped away by Suffian as Selangor went into the break looking comfortable.
The second half started off with both sides having the chance to find the net in the opening two minutes.
Segovia was inches away from adding to his opener before Terengganu midfielder Gabriel Davis saw a rasping effort tipped away Khairul Azhan.
On the hour mark, Terengganu's Ivory Coast forward Tchetche Hermann thought he had equalised after rounding Khairul Azhan. But Selangor captain Razman Roslan came to their rescue by hacking his effort off the line.
Four minutes later, the Turtles did get their equaliser from the penalty spot.
Issey Nakajima-Farran was fouled by Ugo Ukah as he bore down on goal, and referee Khairul Azuan had no qualms pointing to the spot.
The Canadian-born attacker picked himself up to drive a grounder past Khairul Azhan to make it 1-1.
Selangor were stung, and Segovia was again at the thick of things. He hit the bar before laying a low cross that Andik Vermansyah directed just past the bar.
Terengganu came close to taking home all three points in the closing stages, but Khairul Azhan produced two point blank saves to deny Davis.
Other matches saw Kelantan beat Uitm FC 3-1 in Group C, while Pahang and Negeri Sembilan played out a 2-2 draw in Group A.
Selangor: Khairul Azhan Khalid (GK), Andik Vermansyah, Saiful Ridzuwan Selamat, Adam Nor Azlin, Francis Forkey Doe, Razman Roslan (C), Raimi Mohd Nor (S.Veenod 84'), Ugo Ukah, Syahmi Safari (A.Namathevan 43'), Amri Yahyah, Rufina Segovia
Terengganu: Suffian Rahman (GK), Lazaro Vinicius (C), K. Partiban (Ridzuan Abdunloh 75'), Gabriel Davis, Issey Nakajima-Farran, Faiz Nasir, Hafizal Mohamad, Nasrullah Haniff Johan, Firdaus Faudzi, Tchetche Hermann Brice, Azi Shahril Azmi