Second half goals from Zeca and Kim In-sung, who scored in injury time after Urawa's Takahiro Akimoto had been sent off, allowed hosts Pohang to come back and take all three points following Jose Kante's 36th minute opener for Maciej Skorza's side.
The result, coupled with Wuhan Three Towns' surprise 2-1 loss against Hanoi FC, means Pohang have booked their place in the last 16 as Group J winners to leave Urawa chasing one of the runners-up berths in the next phase.
Only the winners of each of the 10 groups across Asia are guaranteed to advance to the next phase, where they will be joined by the three best second-placed teams from each of the eastern and western halves of the confederation.
Urawa are second in Group J on four points and level with Chinese side Wuhan, who they face next in a crucial clash at Saitama Stadium on November 28th.
There was disappointment, too, for two-time champions Jeonbuk Motors as the South Koreans slipped to a shock 2-0 loss at the hands of Lion City Sailors in Group F.
Richario Zivkovic scored both goals for the Singaporean hosts, who move level with Jeonbuk on six points.
The pair trail leaders Bangkok United by four points after Totchtawan Sripan's side were held to a 1-1 draw by struggling Kitchee from Hong Kong.
Willen Mota put Bangkok in front with a spectacular strike from long range in the 27th minute before Kitchee goalkeeper Paulo Cesar saved Mahmoud Eid's second half penalty to stop the hosts doubling their advantage.
Jakob Jantscher capitalised for Kitchee, equalising in the 70th minute and the Hong Kong Premier League champions held on for a point despite seeing Poon Pui Hin sent off two minutes later.
Japan's Ventforet Kofu moved to the top of Group H with a comprehensive 4-1 win over Chinese Super League side Zhejiang FC, the second division outfit climbing over Melbourne City on goals scored.
Former Nigeria international Peter Utaka gave Kofu a 17th minute lead and goals from Masahiro Sekiguchi and Yoshiki Torikai sealed the points in the second half.
Kofu go into pole position after Melbourne City squandered their position at the summit with a 1-0 loss at home against Buriram United, with Goran Causic scoring from the penalty spot four minutes from time.
