Jeonbuk Motors moved top of K League 1 as it defeated Daegu 2-0 and Ulsan was held at home to Busan IPark.
Defending champion Jeonbuk moved in front at home against Daegu after 47 minutes through Brazilian midfielder Murilo Henrique, who beat two defenders and produced an impressive left-footed finish.
Cho Kyu-sung sealed victory from close range with 21 minutes remaining, though his first K League 1 goal was soured slightly as he was later sent off for a second bookable offence in the last minute, having brought down Edgar Silva.
That meant both sides ended the game with 10 men, as Daegu's Kim Seon-min had seen red with four minutes left on the clock for a foul on Kim Bo-kyung.
After three rounds of action, Jeonbuk is the only team left with a 100 per cent record.
Ulsan was hoping to join the leader on nine points on Sunday but ultimately had to settle for a 1-1 draw against Busan.
Lee Jeong-hyeop gave the visitor a surprise 55th-minute lead with a well-taken finish and Ulsan had what it thought was a prompt headed equaliser ruled out for offside against scorer Lee Chung-yong.
That meant it needed a penalty from Junior Negrao, his fifth goal in three games this season, to claim a point 11 minutes from time.