An early second-half strike by Sy ensured the Lions of Chinguetti advance to the quarter-finals as Group D leaders on four points, followed by Angola on two as Mali go home with a single point.
With a qualification to the quarter-finals very much alive for both sides, it was billed to be a tough and equally exciting encounter.
A highly tactical opening half saw very little chances at goal as both teams placed numbers behind the ball with the aim of catching each other on the break.
The Eagles were the first to ask questions of the keeper in the opening minutes after a well-executed transitional play concluded with the target man, Moussa Kone setting up Ibourahima Sidibe in a dangerous position who’s volley went inches wide off goal.
Mali was back in the Mauritanian danger area in the 25th minute, this time through a well taken corner that found the head of Emile Kone, who’s attempt was cleared away from danger by Soukrana Mhaimid to keep the scores level.
Mauritania did well to contain the Malian attack but did very little to threaten them in return, as the two sides went into the break with the scores level.
Coming from the break, it was the Lions of Chinguetti who came back the stronger side and immediately put their opponents on the back foot.
It was as early as the 48th minute when skipper Moulaye Khalil showed off his artistry after eliminating his marker on the edge of the box to unleash a powerful volley that was parried to safety by Germain Berthe.
The pressure continued to mount for Mali and they eventually succumbed to it when a delightful cross from the hard-working Sidi Amar connected well with the header of Mamadou Sy to give his side the unexpected lead in the 53rd minute.
With momentum on their side, the Lions of Chinguetti continued surging forward and could have extended their lead in the 63rd minute after the troublesome Amar found Hemeya Tenji, who’s well taken shot from the edge of the area went just over the bar with the keeper well beaten.
With time not on their side, Mali sent numbers forward in search of the equaliser but found a highly resolute Mauritanian defence who stood firm.
A golden opportunity for the equaliser fell at the feet of Souleymane Coulibaly after Djibril Coulibaly found the defender with a well taken cross but couldn’t compose himself to take a decent strike, as his close-range shot went over the bar in the 80th minute.