Two goals from Dejan Damjanovic gave FC Seoul a 2-0 win over Jeju United in a crunch clash that saw the hosts go top of the K-League.
Jeju arrived at Seoul World Cup Stadium on the back of a six-game winning run that had taken them into first place but they had no answer to the Montenegro marksman.
Damjanovic opened the scoring after 15 minutes. Receiving a pass from Server Djeparov with his back to goal, the former Incheon United star turned and fired a shot into the bottom corner from 20 yards out. The striker sealed the win with eight minutes remaining, side-footing a cross from Choi Hyo-jin into the Jeju net.
"We were always going to lose sooner or later," said Jeju coach Park Kyong-hoon. "What is important now is how we bounce back against Gwangju next week."
The shock of the night came as second-placed Seongnam Ilhwa Chunma were beaten 3-1 at home by bottom club Daegu FC. Cho Dong-keon gave the hosts a first-half lead but a brace from Cho Hyong-ik and a goal from Jang Nam-seok in the second period gave the visitors a stunning win.
K-League champions Jeonbuk Motors made it four consecutive victories with a 2-1 triumph over Busan I'Park to move into second place while fellow Asian Champions League quarter-finalists Suwon Bluewings continued their recent resurgence with a 2-0 win at home to Gwangju Sangmu, new signings Hwang Jae-won and Shin Young-rok got the goals.
Asian champions Pohang Steelers were held to a 2-2 draw by Chunnam Dragons while Gyeongnam FC stay in the hunt at the top with a 3-2 win over Incheon United. Finally, Ulsan Horangi lie sixth following a 2-0 win at home to Daejeon Citizen.