Emiliano Alfaro and Mariano Donda scored either side of a Ricardo Oliveira penalty for Wasl to take a 2-1 lead into the break before the drama unfolded in the final five minutes.
Jazira must have thought they had done enough to earn a share of the points when captain Ibrahim Diaky made it 2-2 four minutes from time but the Dubai club had designs on spoiling the party as Jassim, unmarked at the far post, scored a last-gasp header from a Donda cross to ensure maximum points at Mohammed bin Zayed Stadium, a result that moves them second in Group B, level on six points with leaders Al Dhafra.
"We continued to play the way the head coach had prepared for this game," Gilles Mourisseau, the assistant coach who was standing-in for Bruno Metsu, who did not travel with the team because of illness, said. "The players carried out his instructions to perfection and they also dedicated this result to him. It was an excellent game and the players showed real character to snatch the winner in the dying stages of the game."
Paulo Bonamigo said the defeat has now made the group wide open with four teams - Al Dhafra, Wasl, Dubai and Jazira - with a chance to advance to the knockout stage.
"Our first half our performance was below expectations," he said. "We tried to improve our marking in the second half, particularly on Alfaro and Donda. I think we did better in that half and scored the equaliser but didn't expect for Wasl to score a third goal, which was a bit disappointing when there was a minute left."
Jazira were severely depleted without several key players because of national duty and injuries.
Diaky said they would take this result on the chin and use it as a valuable lesson to prepare for their remaining games.
"It is better we endure such results now so we have time to work on the areas we need to improve, which of course would be our task," he told a post-match television interview.
Jazira had an opportunity to take the lead in the very first minute but Abdulla Qasem completely missed the ball from 12 yards out.
Ahmed Al Shabibi, the Jazira goalkeeper, did well to hold on to a close-range header from Alfaro from a Mubarak Hassan cross from the right.
Alfaro was not to be denied with his second effort. He collected a pass from Maher Passim to blast a shot past a hapless Al Shabibi from close range. It was his 10th goal in six matches, both in the Etisalat Cup and the Pro League.
Jazira's reply was swift. Ricardo Oliveira was brought down by Saud Saied and the Brazilian was spot on with the spot kick to make the score 1-1.
Wasl regained the lead when Donda, the Argentine midfielder, took advantage to score when a poor clearance from Jumna Abdulla, the Jazira defender, fell into his path on 26 minutes.
The second half was a largely uneventful affair until Diaky's equaliser on 86 minutes, but Jassim's late winner ensured the Dubai club bounced back quickly from their humiliating 4-0 home defeat to Dhafra last time out.
Elsewhere in the competition Al Shabab consolidated second spot in Group C after three second-half goals gave them a resounding 3-0 win over Dibba Al Fujairah at the Khalifa bin Zayed Stadium in Al Ain.
Essa Obaid opened the scoring in the 67th minute. Sami Anbar doubled it in the 73rd and Essa Mohammed added the third three minutes later.
Meanwhile Al Shaab redeemed some of their battered pride from last week’s 6-1 mauling by Al Wahda as they held Al Nasr to a 1-1 home draw in Group A.
Younus Ahmed put the visitors ahead in the 27th minute before Shaab cancelled that lead through Nasser Khamis two minutes into the second half. However, Shaab remain bottom of the table.
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