Gary Madine restored the host's advantage before Pereira again leveled with a penalty.
Blackpool went onto win the penalty shootout, with Pereira missing the decisive spotkick.
"The battle was always going to be tough," Allardyce said.
“I saw exactly how tough it was going to be by Blackpool using their assets, playing off big Madine up front, who causes a problem and we have to battle in that area.
"But the most disappointing thing for me was that the goals didn't come from that area, they came from our lapses in concentration.
“Both their goals were getting through the middle after we gave the ball away.
“We came back twice with goals from Semi, good header, and the penalty.
“Extra time came and both sides went out to try and win it.
“We got the best possible start with Butts' saving the first penalty.
“Then from our point of view, I'm hugely disappointed in the penalty takers that missed.
“When you save the first penalty and put yourself one-nil up, at the level we're supposed to be at, we shouldn't have lost at all. I am disappointed with that.
The effort from the players was fine. I've seen players I've not seen before. I'll make a judgment on them in the next few weeks.
“And then we'll move forward as best we can under these restrictions and we'll be working as hard as we can to bring new players in."
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