United went in as favourites to advance to the quarter-final stage of the competition after the 0-0 first-leg draw in Spain last month - but succumbed to a disappointing 2-1 loss at Old Trafford in the return leg.
The defeat to Vincenzo Montella's side was condemned by fans on social media due to the lack of attacking impetus and the Ivory Coast international who was one of the standout performers on the evening took to social media to apologise to the Red Devils faithful.
"We ask the fans for forgiveness following our exit," the 23-year-old wrote on his official Twitter account.
"Last night was terrible and we must all reflect and take note so it doesn't happen again. It's painful, but we have to get right back up, dust ourselves off, and look ahead."