The forward has failed to score in eight months and has been left out of the Nigeria squad for the upcoming African Cup of Nations.
However, Gernot Rohr has explained his decision to the striker and revealed to the Leicestershire Mercury that confidence was a big factor.
He said: "We already had our opinion before the match because we observed them throughout the season and we saw what they did. We had seven training sessions to see the fitness and confidence of the players.
"The choice of dropping two players is really difficult for me.
"I can't take every one of you to AFCON. All the players showed good character, good mentality throughout this week, but we just must drop two players.
"It's so unfortunate and a difficult moment for Iheanacho and Ajayi missing out but they are still part of the team."