Dortmund trailed twice before earning a 2-2 draw against Bayer Leverkusen in the Bundesliga clash at the BayArena on Saturday.
"It wasn't a great performance from us today," the Germany international told reporters. "It was a very intensive game, especially in the first half, but I think we were at fault for both goals, we left ourselves over-exposed and didn't get back quickly enough.
"But we hauled ourselves back into it, when we play our own game, press high up the pitch and win the ball, we do well.
"When we play like we did in the second half, it gets difficult. We're well aware of that and we know we'll need to take it up another level for the cup final."
Dortmund are currently in second place in the Bundesliga, seven points clear of third-placed Schalke 04.