Cup-holders Nigeria, on Thursday, lost by the odd goal to their Sudanese counterparts in an Under-23 Africa Cup of Nations (AFCON) qualifying match at the Al Merriekh Stadium in Omdurman.
The home team scored on the dot of 45 minutes as the Nigeria defence faltered during a counter-attack.
But Stephen Odey, Blessing Muyiwa and Taiwo Awoniyi all had chances to put Nigeria on the scoreline even before then.
Odey fluffed gilt-edged opportunities in the 17th and 48th minutes which would have handed Nigeria the advantage.
Instead, the 1996 Olympics men’s football tournament winners must now overturn a deficit.
They will also then look for the winner when both teams clash in the return and final leg of the qualifying series in Asaba on Tuesday.
The deficit is in no way daunting for the Imama Amapakabo wards.
They had in the earlier round hammered Libya 4-0 at the same Stephen Keshi Stadium in Asaba after losing 0-2 to the Libyans in the first leg in Tunisia.
Nigeria won the second edition of the Under-23 AFCON hosted by Senegal in December 2015, beating Algeria in the final.
Both teams then represented Africa at the Rio 2016 Olympics, where the Olympic Eagles won the bronze medals.
The third edition of the Under-23 AFCON will be staged by Egypt from November 8 to 22.