The BVB boss admitted his side were second best all afternoon but felt they put on an improved showing after the break
Jurgen Klopp was magnanimous in defeat following Borussia Dormund's 3-0 defeat to Hamburg in the Bundesliga on Saturday.
In Mirko Slomka's first game in charge, the hosts put on a sparkling display, taking the lead three minutes before half-time thanks to Petr Jiracek's header.
Pierre-Michel Lasogga doubled the advantage on 58 minutes, before a 50-yard wonder-strike from Hakan Calhanoglu in stoppage-time put the seal on an emphatic Hamburg victory.
"Congratulations to Hamburg for a well deserved victory," said Klopp.
"We wanted to change everything at half-time. We changed the system and we were more lively.
"Hamburg fought, we also fought, but ultimately we have not done enough to bring something away here.
"It was a very modest game for us."