The Buccaneers pressed HAC in the first half - creating chances which they could not convert, but the hosts went on to secure a 2-1 win thanks to two second half goals from Abdoulaye Camara and Boniface Haba, while Justin Shonga netted for Milutin Sredojevic's side.
Here are some statistic takeaways from the match that show how Pirates dominated the match but failed to record a win.
Pirates, who enjoyed a 55.3% ball possession on the night, had a 70.8% pass success rate to Horoya's 66.4%.
The Buccaneers had 187 passes, while the hosts managed to make 114 passes throughout the entire match with Musa Nyatama pulling the strings from midfield for the former.
The visitors had three shots from set-pieces, while HAC had none with Pirates' free-kick specialist Justin Shonga failing to score from a dead-ball.
HAC tried to play long ball counter attacks with speedy forward Ocansey Mandela leading their attack having attempted 78 long balls into the opposition’s half compared to Pirates' 70.
Horoya had 12 shots inside the Pirates box, while the visitors mustered seven shots all match. Boniface Haba scored from close range after the visitors had failed to clear the ball away from their box.
Pirates, who had to win the match to qualify for the knockout stages, had 51% territorial advantage, but they could only score once.
The hosts sat back and launched counter attacks and unsurprisingly they had only 39.4% ball possession in the second half.
Pirates goalkeeper Wayne Sandilands took 11 goal kicks to his Horoya counterpart Khadim N'Diaye's five.
The defeat saw Pirates crash out of the Champions League after finishing third in Group B, while Horoya advanced to the quarter-finals as runners-up.
Bucs' poor away record cost them a place in the last eight having recorded two defeats and one draw. They also struggled at home drawing twice and won once.