An unchanged XI from Saturday’s win over Bournemouth struggled early, conceding in the first minute before equalising through Joao Gomes.
Lacking the energy to mount another comeback, Wolves must now regroup as Pereira assesses what went wrong at Molineux.
On a missed opportunity, he stated: “Of course. Today, I'm frustrated because after three days playing again, we started the first half by conceding a very easy goal.
“Our level of concentration, our focus was not at the level of the game. After, we reacted, we started to play against a good team winning one zero, and we created some situations, and we scored the goal.
“But, when you start the second half in the same way, it's very difficult because in the second half I felt that the team was tired, because the movements, the pressing was not the pressing that we’re used to and when they started with the subs, they had a lot of solutions in the squad.
“For us, it's not the case.”