Lee Bullen reckons Ayr got what they deserved in Kirkcaldy as his Honest Men lost their unbeaten record.
United slipped from the Championship summit on goal difference after going down 3-2 to Raith.
And Bullen insists his side could have few complaints - because they failed to put in a full shift.
He said: "You can't play for 30 minutes like we did and expect to get something out of the game.
"Credit to the boys for showing character in the second half to come back and I thought we had the momentum at that point.
"But we then went through a lull and seemed to sit back again and that's the disappointing aspect for me.
"When things go against you, I am happy to take the responsibility on the chin.
"The players have been brilliant all season and we've been due a setback - I didn't see it coming here but this was the right result over the piece.
"We're still joint top of the league and there's a lot to be positive about moving forward.
"You've got to be at 100 per cent in this league or you get results like that but we have a chance to put it right in the games coming up and prove that our form so far has been no flash in the pan."
Bullen made two changes to the side which won at Morton with defenders Alex Kirk and Jordan Houston dropping out, which meant starts for Sean McGinty and Nick McAllister.
But Ayr looked all at sea from the start and were cut open early on as Kyle Connell slotted home from 12 yards.
Dylan Easton headed just over soon after as they went for the kill in the opening stages with United at sixes and sevens.
But they eventually got to grips with the game as the first half wore on and Dipo Akinyemi rattled the woodwork with a free kick as they went close to a leveller.
But just as Ayr were pushing, they were caught with a sucker punch from their own corner kick as Raith blitzed to the other end and doubled their lead through Sam Stanton.
That sparked a triple change at the break with Houston, Josh Mullin and Brad Young all introduced.
And Young made an immediate impact when knocking home an Akinyemi centre just six minutes after the restart.
Suddenly it was all Ayr and the tide had firmly turned when Andy Murdoch crashed home a Mark McKenzie knockdown to level the game with 21 minutes still to play.
There looked only one winner at that stage but Ayr couldn't push on and Rovers skipper Scott Brown rammed home a late winner after United had failed to clear their lines.
Raith boss Ian Murray said: “We reacted very well. I’ve seen it many times when you’re 2-0 up and you lose the game 3-2.
“It really says a lot about the players’ character. The determination and courage was great."
