Pohang had to settle for a point against fellow title rivals Jeju United on Saturday after playing out a goalless draw away from home.
But Pohang were not the only team that drew over the weekend, with four of the six fixtures ending all square.
With second-placed Jeonbuk Motors also winning - accounting for lowly Busan I'Park 2-0 - Pohang's lead at the summit was reduced to two points after 13 rounds.
But Hwang Sun-Hong's men will have the chance to maintain their advantage and extend it against 2012 K.League champions Seoul at the Steelyard Stadium - a preview of the pair's upcoming AFC Champions League quarter-final tie in August.
Seoul have experienced an inconsistent run of results, with just two wins from nine games leaving them in ninth position on 13 points - five above cellar-dwellers Incheon United.
Their latest a result - a come-from-behind 2-2 draw at Chunnam Dragons - further highlighted the club's deficiencies after conceding two goals inside the opening 13 minutes and they will be seeking an improvement against the competition's pacesetters.
In other midweek fixtures on Wednesday, Jeonbuk Motors and Jeju United will go head-to-head at Jeonju World Cup Stadium.
The clash will pit second against third, with Jeonbuk two points clear of Jeju United, who are unbeaten in five games after three consecutive draws.
History is against Jeju United, having only won one of the past nine meetings between the two clubs, though that solitary 2-0 victory was the most recent clash in April.
Elsewhere, fourth-placed Chunnam Dragons entertain second-bottom Gyeongnam at Gwangyang Stadium.
Gyeongnam are winless in nine games and have only won two of their past 36 K.League away fixtures.
Suwon Bluewings are at home for the second consecutive game as they host Ulsan, with both teams level on 20 points.
Meanwhile, basement club Incheon United welcome Seongnam to Sungui Arena Park and Busan I'Park travel to Sangju Sangmu.