Liverpool won 1-0 on Sunday thanks Alexis Mac Allister's late goal.
“We are creating,” Pereira said. “In the first half, we crossed a lot of balls into the box and tried to shoot a lot. We tried to get one-on-one situations.
“Every time, we were ready to attack and not allow them chances. We played very good football. The second half was not the same because it was impossible to have the same energy.
“Frustrated. Frustrated inside. Angry with football. It is time to keep the mentality and come back stronger and with confidence to face the future.
“First half, we played the way we did in Istanbul but we didn’t score. We created two good chances to score but we didn’t.”
Pereira couldn't fault the effort of his players on the day.
“I’m very frustrated today and it is very difficult to go inside the dressing room,” said the Portuguese. “What can I say to them? They did everything to try to win.
“We wanted to win the game. In the end, it was not one point, it was zero.
“This is football. We don’t have time to complain, we need to focus on the next game.”