Ivory Coast surprised Nigeria 1-0 in Cairo on Saturday in the Group B opener at the Under-23 Africa Cup of Nations - the continent's qualifying tournament for the 2020 Tokyo Olympic Games.
Later, South Africa - who came to Egypt with a severely depleted squad - drew 0-0 with Zambia in the second Group B match.
The tournament got underway on Friday with hosts Egypt beating Mali 1-0 and Cameroon and Ghana drawing 1-1 in Group A.
On Saturday, Ivory Coast's Silas Gnaka converted a penalty after Olisa Ndah committed a foul that resulted in him being sent off, leaving Nigeria to play the final 20 minutes a man short.
Nigeria lacked captain Azubuike Okechukwu and Taiwo Awoniyi after their Turkish and German clubs refused to release them before the international window.
Many European clubs did agreed to free players for the tournament, even though it started and will finish outside the window.
Meanwhile, South Africa and Zambia provided plenty of free-flowing football only to be let down by poor finishing.
South Africa arrived in Egypt with just 12 players, and lacked six of the 21-man squad when they faced Zambia due to some domestic clubs taking a hard line on releasing players.
The eventual finalists and the winners of the third-place play-off will represent Africa at the 16-nation Tokyo Olympics football tournament.