KUALA LUMPUR: Selangor interim coach Abdi Hassan admitted that the 1-0 defeat to Jeonbuk Hyundai Motors was a "bitter pill to swallow" in Thursday's AFC Champions League 2 (ACL2) match at Jeonju World Cup Stadium.
In the Group H match, Jeonbuk's Tiago Orobo scored the only goal with a header from a corner kick in the 22nd minute.
With the victory, the Korean side now lead the standings with nine points, two more than second-placed Selangor.
Abdi said a single lapse in concentration proved costly for the Red Giants.
"It's a tough loss to accept. We were caught off guard by a set-piece — something we'd worked on but didn't execute when it mattered. We gave them an opportunity and paid the price," said Abdi at his post-match press conference.
Selangor came close in the second half, but striker Ronnie Fernandez's powerful shot struck the crossbar.
"Ronnie almost found the back of the net. If that shot had gone in, it could have changed the outcome. However, Jeonbuk deserved the win. They were solid and efficient in both attack and defence," said Abdi.
Selangor's remaining group matches are against Thailand's Muangthong United at home on Nov 28 and DH Cebu in Manila on Dec 5.