Ulster director of rugby Les Kiss identified his side's inability to capitalise on their numerical advantage as a key reason for Friday's loss to Saracens at Ravenhill.
Saracens back-rowers Michael Rhodes and Billy Vunipola were sent to the sin-bin either side of half-time but Ulster could only add three points during that 20 minute period.
Kiss' charges raced into a 9-0 lead in the first-half but Saracens struck back and secured a 27-9 bonus-point win thanks to tries from Chris Wyles, Alex Goode, Duncan Taylor and Billy Vunipola.
"The first 25 minutes, we certainly positioned the game where we would have liked it," said Kiss.
Sarries were then reduced to 14 men for the first time, when Rhodes was yellow carded for a careless challenge on Andrew Trimble, but Ulster could only add three points during the next 10 minutes.
"It was disappointing in that 10-minute period in the first half that we didn’t take advantage and put the foot on the throat," added Kiss.
"A couple of back-to-back errors gave them access to our end, and they did well to get the try.
"Then 9-5 is very different to 9-0 at half-time and they certainly would have built some confidence on that in the second-half."
Vunipola then spent time in the sin-bin 15 minutes into the second-half after a dangerous hit on Iain Henderson but once again, Ulster failed to capitalise.
"We had a chance in the second half to get up there and assert ourselves we just didn’t work hard enough to make the opportunities come our way," said Kiss.
"We spoke in the dressing room, when they go down to 14 they seem to have lifted and we seemed to… not play the type of football that we probably planned to.
"If we had got to that space, maybe we could have hurt them, but it wasn’t to be.
"They kicked the corners really well, we didn’t cover the grass well, we didn’t take advantage of grass that was available to us and turn them around."