Al Sadd had looked on course for a first win in three matches when a brace from Hasan Al Haydos (27 and 80) saw them leading 2-1 at struggling Al Rayyan heading into stoppage time.
However, the home side, who had already equalised once through Sayaf Al-Korbi's 51st-minute strike, snatched a last-gasp leveller through Oumar Bari to earn a share of the points.
That was a blow for Al Sadd but it did not cost them top spot as second-placed Lekhwiya were held goalless at home by Al Siliyya, while out-of-form El Jaish in third slumped to a 2-1 home defeat to Al Arabi.
Wanderley netted an 89th-minute winner in that match to help fourth-placed Al Arabi move to within three points of their opponents, who have now lost four league games on the trot having previously been unbeaten in their opening 10 matches.
Wanderley's winner was his second goal of the match, with his 32nd-minute opener being cancelled out soon after by Wagner Ribeiro's goal.
In the day's other game Al Khrityat won 3-2 at Al Wakra. Youssef Kaddioui (five), Jaycee Okwunwanne (eight) and Mahmoud Saad (57) were on the mark for the victors while Sebastian Saez (35) and Hussein Yasser (55) replied for Al Wakra.