Jeonbuk had won its first three matches of the new campaign to claim top spot, but met its first major bump in the road when Korea Republic international Hong was dismissed after just 15 minutes on Saturday.

The former Augsburg defender, who scored in the matchweek two win over Busan IPark, tugged down Cho Jae-wan after a poor first touch on the edge of his own area.

Boss Jose Morais replaced striker Lars Veldwijk with defender Kim Min-hyeok as Gangwon quickly seized control, but the decisive goal arrived eight minutes before half-time.

Ko Moo-yeol headed Kim Kyung-jung's teasing right-wing cross beyond Song Bum-keun from close range to clinch the points.

Jeonbuk's defeat gave unbeaten Ulsan Hyundai the opportunity to move to the summit of the primitive league table with victory over previously pointless basement side Gwangju.

But Ulsan could muster only a 1-1 draw having fallen behind after Eom Won-sang steered past Jo Hyeon-woo 12 minutes in when team-mate Felipe Silva was crowded out inside the area.

A scrappy equaliser followed only after a lengthy VAR (video assistant referee) delay, with Lee Han-do getting the final touch to beat his own goalkeeper as an awkward cross drifted through the area.

Elsewhere, Saturday's other fixture between Busan and Suwon Bluewings ended goalless.