Nigeria will face hosts Senegal in the semi-final of the U23 AFCON on Wednesday after they held Algeria to a goalless draw in Dakar. The other semi-final will be between Group B winners Algeria and South Africa, who finished as runners-up.
Nigeria finished runners-up in Group B, while Algeria won the group by virtue of a better goals difference after both teams finished on five points each.
Mali edged past Egypt 1-0 in the other Group B match in Mbour to finish third with three points with the Young Pharaohs bottom on two points.
The top three teams will qualify automatically for the Rio Olympics next year with the fourth-placed team vying for a place in Brazil in a playoff.
In Dakar, the match between Algeria and Nigeria was always going to be a cagey affair after both teams also battled in a final group game at the inaugural tournament in Morocco four years ago with the West Africans winning 4-1.
Siasia dropped struggling Liverpool loanee Taiwo Awoniyi for Warri Wolves striker Kufre Ebong for the crunch encounter.
Awoniyi, who is on loan to Germany from EPL side Liverpool, was one of the stars as Nigeria won a seventh African Youth Championship in Senegal in March, but has struggled to find his feet thus far on this occasion.
In a half of very few openings, Nigeria had two chances to take the lead in Dakar – first an audacious 30-yard lob forced goalkeeper Sahli to tip it for a corner in the 13th minute and in the 34th minute Oghenekaro Etebo’s free kick was barely kept out by the Algeria shot stopper.
Algeria striker Draoui threatened the Nigeria goal after 26 minutes but goalkeeper Emmanuel Daniel came off his line to cut out the danger.
That was a minute after their effort was ruled offside by the referee.
In the second half, Etebo was denied by a big save by goalkeeper Salhi, who dived full length to push away a goal-bound effort by the near post.
Algeria also had their moments after the interval, but they did not have the cutting edge to get a goal in this contest.