Edinburgh boss Alan Solomons believes a lack of discipline was the reason for his side's loss to Ospreys at the Liberty Stadium on Friday.
Solomons' side held a 13-6 lead late in the first half but the Ospreys' struck back with a Sam Davies try to draw level at the interval before dominating the second half to clinch a 27-13 victory.
When asked what caused his side to fade so badly, Solomons told the BBC: "The biggest factor was discipline.
"We talked about it at half-time.
"We said we have dominated possession and territory, we've got to keep doing that, but our discipline wasn't good."
Edinburgh's skipper Neil Cochrane was yellow carded in the 65th minute for a foul in the ruck. Solomons feels that decison played a crucial role in the end result.
"I thought we played really well the first half," he added.
"We had possession and territory and missed two kicks at the posts that perhaps we should have got, then they got a very good try.
"So, after dominating territory and possession, right at the death, we go in 13-13.
"The second half was the reverse. They dominated territory and possession and, ultimately, when Neil went off with a yellow card, that killed us.
"We gave away a lot of penalties, plus a yellow card, and I think that was the difference in the second half."