Borussia Monchengladbach coach Marco Rose was left frustrated and annoyed after his side's 1-0 loss to Freiburg in the Bundesliga on Friday.
Nils Petersen's 58th-minute goal lifted Freiburg to a surprise win and left Gladbach, who finished with 10 men after Alassane Plea's red card, in fourth in the table.
Rose rued the defeat as his team were left in danger of falling out of the Champions League qualification places.
"I'm incredibly frustrated after any defeat. Of course they're even more annoying when you're pushing hard for your goals at the end of the season and the way the game played out doesn't help either," he said, via the club's website.
"We had a very good first half and then in the second half we defended one set-piece very badly and got a red card, so it's a defeat that we could certainly have done without.
"We showed a lot of desire, invested a great deal and dominated Freiburg. We knew that they're dangerous from set-pieces, so we shouldn't even be giving away the free-kick in the first place.
"The lads have high aspirations and are of course disappointed with the result as well. We have to digest it first and then come Monday we will start to look ahead to the game in Munich."
The game's only goal came via Petersen, who headed in a Vincenzo Grifo set-piece, before Plea picked up a second yellow card with 23 minutes remaining.
Borussia Monchengladbach goalkeeper Yann Sommer lamented the way his side switched off for Petersen's winner.
"We played well in the first half and had a number of good chances. Unfortunately, we didn't get a goal. After the break, Freiburg made the most of a free-kick and took the lead," he said.
"The result is obviously anything but ideal, but we will push on. We invested a lot into the game, playing with real energy and power.
"We actually put in a good performance I thought, but we went to sleep for one minute. We still have four more games and want to bounce back next week in Munich by picking up points."
Borussia Monchengladbach make the trip to Bayern Munich on June 13, while eighth-placed Freiburg visit Wolfsburg on the same day.