Defending champions Nigeria suffered a 1-0 defeat to Ivory Coast in their opening match at the Under-23 Africa Cup of Nations in Cairo.
Silas Gnaka's penalty 19 minutes from time was enough to get Ivory Coast's Group B campaign off to the perfect start at Al-Salam Stadium.
Olisa Ndah was sent off for Nigeria after he committed a foul inside the penalty area and Gnaka converted the resulting spot-kick.
Nigeria, the Olympic bronze medallists, were unable to find an equaliser in a disappointing start to the defence of their title.
They struggled to create many clear-cut chances throughout and were made to pay by Gnaka, whose penalty was the only moment of quality in a dour contest.
In the other match played today, South Africa and Zambia played out a goalless draw.
Nigeria will hope to bounce back from the defeat when they play Zambia on Tuesday (November 12), while Ivory Coast take on South Africa in their second group match.
Three spots in the men's event at next year's Olympic Games in Tokyo are up for grabs at the tournament.
The finalists and the winner of the third-place play-off will qualify for Tokyo 2020.