The Pharaohs boss was speaking after their 2-0 win over DR Congo on Wednesday, a victory which was secured courtesy of first-half goals from captain Ahmed Elmohamady and Mohamed Salah, which took them into the Round of 16.
For a second successive game, however, the host nation seemed to fall off after the break, which Aguirre revealed is a cause for concern.
"I'm trying to find the reason of this drop in the second half. We have to play the full 90 minutes with the same performance," Aguirre told the post-match news conference.
Be that as it may, the Mexican coach was pleased with the victory and explained why he could ring the changes for their final game against Uganda on June 30.
“We managed to control the game in the first half and succeeded in sealing the victory in that part of the game. We now have six points and hold the group leadership," he added.
“We were fully concentrated and we had the chance to score more goals despite the team's drop in the second half.
"I am considering introducing new faces against Uganda," he added.
"Many players appeared exhausted against DR Congo and they need to rest, but I will not reveal their names now."
After two games, Aguirre’s troops top Group A with six points, two more than second-placed Uganda who they face in Sunday’s final group game. Zimbabwe and winless DR Congo are third and fourth, respectively.