Cornish Pirates boss Ian Davies says ill-discipline "came back to haunt" his side in their 36-15 British and Irish Cup semi-final defeat at London Welsh.
They failed to score a point in the second half as Rob Elloway, Matt Evans and Joe Atkinson were yellow-carded.
"The communication was there, we just weren't reacting to what he (the referee) was saying," Davies said.
"The cumulation caught up with us with three yellow cards - you don't often see that, but they were justified."
Pirates had beaten their Championship rivals in all three of their previous meetings this season.
Evans and on-loan Exeter scrum-half Stu Townsend scored tries for the Cornish side, who will lose head coach Davies in the summer due to budget constraints.
"In that first half that's all that was keeping them in the game, our ill-discipline," he told BBC Radio Cornwall.
"Ill-discipline came back to haunt us - it was one bridge too far.
"There have been some dark days and some long days, so to get to a final would've been great, but we haven't achieved that."