Fuming Leicester coach Richard Cockerill admitted there was a stunned silence in the home dressing room after London Irish fought back to secure a 24-24 draw.
Leicester led 13-7 at half-time and looked to be home and dry with a second-half try from centre Horacio Agulla but Leicester turned down kickable penalties as they looked for a try bonus point and Irish full-back Tom Homer booted a penalty and converted tries from replacement wing Adam Thompstone and Matt Garvey to complete a remarkable comeback.
"It is hugely disappointing," said Cockerill. "We put ourselves in a position to win it. The penalty count was massively in our favour and we didn't take advantage of it. We have nobody but ourselves to blame for what has turned out to be a poor result."
He added: "We made poor mistakes across the board in that last quarter and it cost us the win.
"They played well and defended well but we got what we deserved. At 24-7, we had to play in the right areas of the field and control the ball.
"But we played a lot of time in our own half, had sloppy pieces of play and we let them back in the game. We have to do better. We got charged down from a box kick and then two minutes later we get charged down again for them to score and draw the game. Across the baord, everyone was to blame."
Irish head coach Toby Booth praised his men for fighting back against the odds.
He said: "It was a tough contest and I think the most pleasing thing is to come back from such a deficit. It speaks volumes about the team.
"That is fantastic and, if you have that type of effort and belief, it bodes well for you kicking on when things are tough.
"What is remarkable for me is we have come here and got something out of the contest with a line-out that struggled in particular and the penalty count was 17-6. We also contributed 17 turnovers. So, to do that at Leicester and still get something out of the game, shows how well we defended."