Sudan defeated Nigeria 1-0 in their U-23 Africa Cup of Nations qualifying match at the Al Merriekh Stadium in Omdurman on Thursday.
The Sudanese team scored in the 45th minute against the run of play.
The goal came after the Nigeria’s defence faltered from a counter-attack.
Before conceding, Nigeria were in control but Stephen Odey, Blessing Muyiwa and Taiwo Awoniyi failed to convert their chances.
Odey missed opportunities in the 17th and 48th minutes that would have handed Nigeria the advantage.
With the outcome of Thursday’s match, Nigeria must overturn the deficit and then look for the winner when both teams clash in the return and final leg of the qualifying series in Asaba on Tuesday.
Imama Amapakabo’s boys had hammered Libya 4-0 at the same Stephen Keshi Stadium in Asaba after losing 2-0 to the Libyans in the first leg in Tunisia.
Nigeria won the second edition of the U-23 Africa Cup of Nations hosted by Senegal in December 2015, beating Algeria in the final, and both teams then represented Africa at the Rio 2016 Olympics, where the Olympic Eagles won the bronze medals.
The third edition of the U-23 Africa Cup of Nations will be hosted by Egypt from November 8 to 22.