Ulster director of rugby Les Kiss admitted the 33-17 Champions Cup defeat at Saracens was "an opportunity lost".
Mark McCall's teak-tough Sarries ground out the win that guaranteed them a home quarter-final and left the visitors facing a nervy final round of games next week.
Ulster take on out-of-contention Oyonnax at Kingspan Stadium requiring a convincing win to have any hope of progression, and Kiss said they only have themselves to blame after a patchy display at Allianz Park.
“The second half was disappointing," Kiss told RTÉ Sport. "I thought in the first half we did enough to be better than where we were but when you get down that end of the pitch, you back yourself to go to the sideline and you don't quite know what you need to do at the setpiece to set it up then it’s costly against a team like Saracens.
"We only have ourselves to blame. It’s a hurting dressing room. It was an opportunity lost in a lot of ways because of what we did early in that first half but we just didn’t get back to that part of our game that we knew we could play to."
Luke Marshall gave the visitors the perfect start when he crossed for an early converted try but Sarries struck back with two Owen Farrell penalties and a Billy Vunipola try to lead 13-7 lead at half-time.
Duncan Taylor, Maro Itoje and Schalk Brits crossed after the break to wrap up the win, and Kiss was left fuming at the manner in which Ulster coughed up those points.
“You’ve got to be able to take the good work you’ve done and then build up on it," he said. "It’s not like we started the second half really poorly but we just kept reacting to the pressure they were putting on us rather than having the composure to keep our game together."
