The Serbian center back feels BVB could have progressed to the semifinals had the team taken its chances in Wednesday evening's encounter.
An Arjen Robben strike was the difference between the two sides, and meant Dortmund's cup adventure came to an end in the quarterfinals, but Subotic feels BVB could well have emerged victorious with a bit more luck.
"I think we’ve got to be frustrated with ourselves because in the second half we deserved to score at least one goal and we didn’t," Subotic told Bundesliga.com. "It could all have been different if we had found that one goal and I think in the second half we definitely should’ve hit the net at least once. Then we would’ve gone into extra time and who knows what might have happened.
"I think the main difference was that in the first half they had a lot of chances and they scored a dream goal. After the break we had some great opportunities, but we just couldn’t capitalize on them."
Dortmund will be looking to return to winning ways on Saturday when it takes on Hannover.