Ulsan Hyundai retained their one-point lead at the top of K-League as they and Pohang Steelers both posted victories on Tuesday.
Ulsan routed mid-table outfit Jeju United 4-0 at home, with a Kim Shin-Wook double and goals from Kang Min-Soo and Yong Lee helping them to an 11th win of the season.
Steelers, meanwhile, were forced to work far harder for their three points, with a Lee Myeong-Ju goal on the stroke of half-time earning a 1-0 victory against Suwon Bluewings.
Pohang are now also five points clear of third-placed Jeonbuk Motors, who still occupy the final AFC Champions League qualification berth despite their disappointing draw with Daejeon Citizen.
Jeonbuk were in fact forced to come from behind after Jung Seok-Min put rock-bottom Daejeon ahead, but did so thanks to Leonardo's second-half goal.
Just above Daejeon, Gangwon remain stranded five points from safety after they suffered a 1-0 home defeat to Seoul inflicted by Kim Hyun-Sung.
And their misery was compounded as they were leapfrogged by Daegu, who earned a crucial 1-0 victory against Seongnam to move into 12th by virtue of goal difference.
Daegu's hopes of escaping the relegation mix entirely were also boosted by 11th-placed Chunnam Dragons' 2-1 loss to Busan I'Park.
Elsewhere in the K-League, Gyeongnam saw off Incheon United 1-0 thanks to Milos Bosancic's 42nd-minute penalty.