Pearson's side, who are bottom of the top flight, fell to a 2-1 fifth round defeat at Villa Park as they struggled to make their first-half dominance count before finding themselves on the back foot after the break.
Andrej Kramaric's late header proved a consolation following strikes from Leandro Bacuna and Scott Sinclair, leaving Pearson frustrated at his side's hit-and-miss nature.
"The reason we are having a frustrating season is because we don't reproduce performances," he told BBC Sport.
"All but one player was in the side who started against Arsenal [on Tuesday], which was a good performance, and [against Villa] we did not do well enough for long periods.
"We have to make sure our performances are more consistent. That is what is more annoying.
"Players, when they are in the side, have to make sure they produce performances that make it difficult to make changes."
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