Aziz Ibrahimov scored the only goal after 38 minutes to inflict just a fourth defeat of the season on Jiangsu.
They will lose top spot in the table on Sunday if Guangzhou Evergrande win their game in hand against Shandong Luneng.
Beijing Guoan were beaten 3-1 by Dalian Aerbin to leave them outside the top three.
Seydou Keita gave Aerbin a 37th-minute lead with Peter Utaka's brace after 45 and 74 minutes putting them firmly in the driving seat.
An own goal from Wang Hongyou got Beijing on the scoreboard but it came too late for the visitors.
Shanxi Zhongxi remain second from bottom in the standings following a 1-0 loss at home to Tianjin Taida, whose goal came from Vladimir Jovanicic.
Guizhou Renhe inflicted more misery on Shanghai Shenhua with a 4-2 win.
Rafa Jorda, Dino Djulbic, Chen Jie and Sun Feng were on target for the hosts, with Joel Griffiths and Didier Drogba replying for Shanghai.
James Chamanga scored twice for Dalian Shide but it was not enough to stave off a 3-2 defeat at Liaoning.
Yu Hanchao, Milos Trifunovic and a Peng Lu own goal secured the points for Liaoning.