Ulster director of rugby Bryn Cunningham rued his side's second half performance against Bordeaux-Begles on Sunday.
Bordeaux were able to grab three tries in the dying minutes to win 28-13 at Stade Chaban-Delmas.
"I'm stunned. I thought at half-time we looked to be in the driving seat. The opening 10 minutes we weathered the storm pretty well and started taking control of the game," Cunningham told BBC Northern Ireland.
"We played a lot of territory, went through the phases and we were good for our half-time lead. We should have been more out of sight but didn't take some chances, but at least we were looking positive and had stamped our authority on the game.
"The second half was nothing short of atrocious. I am absolutely gobsmacked at how we played – our defence on our own line was outstanding at times, and we showed a lot of heart there, but we stayed camped there.
"We only spent a minute in the opposition half in the second half – it was incredibly disappointing. And then to throw away the chance of a losing bonus point in the end when we fumbled the ball and they ran the length of the pitch, just rubbed a bit of salt in the wounds.
"All in all it was massively disappointing. We knew we needed to get something out of this game given the tight nature of the pool."