FC Seoul slipped to only their third league defeat of the season after going down to a last-minute goal in a 3-2 loss at lowly Incheon United.
Seoul, who would have moved back to within a point of K-League leaders Jeonbuk Motors with a victory, took a 33rd-minute lead through Kim Jin-kyu, but Incheon battled back to go 2-1 up following a brace from Han Kyo-won.
Visitors Seoul drew level at 2-2 almost immediately thanks to a Ha Dae-sung goal, but it would be Incheon celebrating at the end after Ferdinando scored a 90th-minute winner for the hosts.
Fourth-placed Ulsan Hyundai took advantage of Suwon Bluewings' defeat by Jeonbuk Motors yesterday as they closed the gap on the third-placed team to just one point with a 2-1 away win over Gangwon.
Lee Keun-ho netted a 54th-minute winner for the visitors after Gangwon's Kim Eun-jung had cancelled out Kim Shin-wook's 40th-minute opener.
Fifth-placed Jeju United and Busan I'park in sixth also picked up three-point hauls, beating Daejeon Citizen 4-1 and Chunnam Dragons 3-2 respectively.
Quickfire goals from Junior Santos and Song Jin-hyung in the 27th and 28th minutes put Jeju in control against second-bottom Daejeon and another rapid double from Seo Dong-hyun (63) and Song (66) saw them end the game as a contest. Daejeon netted an 89th-minute consolation from a Yuta Baba penalty.
Busan's victory came courtesy of an 83rd-minute winner from Han Jeong-hwa. Busan's other goals came from Bang Seung-hwan (29) and Yoon Dong-min (45), with Chunnam notching through Faria da Silveira's first-minute penalty and Flavio's 75th-minute strike