Munster's bonus-point win over title rivals Glasgow Warriors the previous week had seemingly put Foley's side in pole position in the battle for a play-off place going into the most critical stage of the campaign.
But defeat to the Ospreys now leaves them just four points ahead of fifth-placed Leinster, and it could have been a lot worse, had Matt O'Connor's side not also lost in Wales on Saturday evening.
Dave O'Callaghan even found his way into the bin against Ospreys, but Foley insisted he could have no complaints.
"It's baffling for us where that performance came from," admitted Foley. "It wasn't in our training in the week, it wasn't in our preparation but then to go out and give away that many penalties in the game, you are going to get punished.
"We conceded one try in the game when we had a player in the sin bin but I think we had six penalties to zero at that stage.
"I can't complain about the referee, I thought the penalties were fair and within reason, it was down to our lack of control and you expect to get punished off the park by the referee, and we did."
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