United won 4-2 on the day, having jumped to a 3-0 lead before Danny Welbeck and Babis Kostoulas struck to pull the score back to 3-2 before Bryan Mbeumo scored his second for the game.
"It is disappointing. We made too many mistakes and like this, you cannot win the game,” admitted Hurzeler.
"I felt it all the time that there was something in the game for us. We are consistently there. We worked hard, we had chances, but the main thing was after our too easy mistakes, it cost us energy.
“We were always dangerous in their final third but when you give away four presents you can’t win a game. United pressed man to man so you have to do the small executions well and we weren’t at our highest level.
"In the end it is about execution and our execution wasn't right, so we have to start in training taking every pass and every touch seriously. We have to improve.
“Like I said, the character was good, the personality and the belief was there. We never gave up but the main thing is we made too easy mistakes.”