Forwards coach Jonathan Humphreys says he cannot explain the dip in form which has left the Ospreys' Magners League play-offs hopes hanging by a thread.
The defending champions failed to win for a fourth straight match on Saturday as Munster snatched victory in Swansea with the last kick of the game.
"Our destiny was in our own hands a few short weeks ago," said Humphreys.
"There's only one team to blame and that will be us. We'll have a good look at that at the end of the season."
The 20-22 defeat leaves the Ospreys outside the play-off places in fifth place, and a bonus-point victory away to Aironi in the final game of the season will not be enough to finish in the top four if other results go against them.
Since the end of the Six Nations, the Ospreys have been in free-fall, losing to Edinburgh, the Dragons and Munster, while drawing at home to Cardiff Blues.
And Humphreys, who faced the media in place of head coach Scott Johnson after Saturday's defeat to Munster, conceded: "Our form has certainly dipped off.
"We were second coming into this last block and to fall out of contention is very, very disappointing. We tried to find ways to carry on our momentum.
"We managed to do it last year, we did it very, very well last year. But this year we just haven't managed to do it."
With Wales internationals James Hook, Lee Byrne and Craig Mitchell leaving, as well as high-profile players such as Marty Holah and Jerry Collins, the Ospreys have already started the rebuilding work.
According to former Wales captain and ex-Sale Sharks coach Kingsley Jones, the region has reached a crucial crossroad and must set the correct tone with their new acquisitions.
"The ambition from the people at the top is there," he said on BBC Wales' Scrum V programme. "The investment, the people they've brought there - there's no doubt they want to be winning Heineken Cups.
"Sometimes you can't just buy that formula. Sometimes you create your own problems by having 30 of the best players."
He added: "They need to go with the likes of Alun Wyn Jones and Ryan Jones as the enforces in the team that create the environment and the culture."
Victory against Munster seemed to have been secured when Hook, playing his final home match before moving to Perpignan, slotted over a 76th-minute penalty.
But Collins, another high-profile name leaving at the end of the season, conceded a needless last-minute penalty on the halfway line, giving the visitors a perfect attacking platform.
The home side were then caught offside as they rushed to charge down Ronan O'Gara's drop-goal attempt, and the fly-half made no mistake from the resulting penalty in front of the posts to leave the Ospreys' season in potential ruin.
"I'm bitterly disappointed," said Hook after saying his farewell to the Liberty Stadium faithful.
"We knew we had to win but it didn't happen. We played with a bit of intent, especially in the first half. Munster, as they always do, grind you down and they got their penalties.
"O'Gara kicked his goals as usual and punished us.
"I thought my kick had won it but silly penalties let them back into it and they probably deserved to win in the end."
A victory or a draw for Cardiff Blues in one of their final two games of the season against the Scarlets and Dragons, and one point for Ulster away to the Dragons on the final weekend will see the Ospreys finishing outside the play-offs.
And Hook, who said he has "superb memories" and "great mates" from his seven seasons at the Liberty Stadium, said he harbours little hope of extending his Ospreys career for a few more games.
"It could happen but we didn't want to get into this position," said Hook, who will miss Wales' Test against the Barbarians on 4 June to get married.
"We wanted to go through on our own merit. Hopefully we can do it but Cardiff Blues are a quality side and it's going to be tough for them to lose two games.
"We know the Dragons are a good side, they've turned us over on several occasions. So hopefully they can do us a favour but the Blues are a good side and are no push-overs."