As the first round of competition ended with four games on Sunday, Jeonbuk were the day's big winners with a convincing victory on the road.
Brazilian Leonardo fired the winners in front as early as the fifth minute before Lee Dong-Gook doubled their advantage just before the break.
Belgian Kevin Oris added polish to the scoreline 20 minutes from time with a third goal.
Daejeon scored a consolation goal through Jeong Shung-Hoon but it mattered little as Jeonbuk Motors recorded an impressive win.
Suwon Bluewings are second on the table after a 2-1 success at Seongnam Ilhwa, ending a good week for the winners.
Suwon won an important point against the Central Coast Mariners in a 0-0 Asian Champions League draw in midweek and backed it up with a victory triggered by Seo Jung-Jin's early goal.
Kim Tae-Hwan levelled for Seongnam on 23 minutes and it looked like it might be enough to secure a draw for the hosts.
Cho Dong-Geon had other ideas though and bagged the winner on 72 minutes for the Bluewings.
Other results saw second-half goals from Ianis Zicu and Bae Hyo-Sung earn Gangwon a point in a 2-2 draw against Busan I'Park while Incheon United and Gyeongnam played out a goalless stalemate.