Celtic are second in Group G with four points, a point ahead of Spartak, who defeated Benfica 2-1 at home to get their campaign back on track.
Barcelona are top of the section having won all three games thus far.
“Barcelona have opened the group and nobody can get automatic ticket after Barcelona. We will work harder because we can still make it out of this group. But Celtic are the major threat to us now, but we will do it," said Emenike.
The Nigeria international striker missed the home win over Benfica as a result of a waist problem. He hailed the spirit of his club to win their first points despite having an injury crisis.