PSV loanee Marcus Berg admits he does not know why he has been unable to hit his top form in Eindhoven this season.
The Swedish striker has spent the campaign on loan at Philips Stadion from Hamburg but has failed to make an impact at the Eredivisie club, scoring just eight goals.
That haul is a stark contrast to the 37 strikes he netted during two seasons with FC Groningen between 2007-09.
And Berg says he cannot explain why he has failed to reach the level of performance he produced during his last stint in Holland.
"I've missed too many chances, everyone knows that," Berg told Algemeen Dagblad.
"I'm not a worse player than I was two years ago. There is not a culprit."
Berg's failure to find the back of the net has prompted a hostile reaction from the PSV fans, and the striker admits the jeers do not help his cause.
He added: "The first time I was booed, it hurt.
"Against Vitesse (when he scored) I only thought, 'why?'. I also have good games and always do my best."
Berg will return to Hamburg at the end of the season, but the Swede insists he is focused only on helping PSV to a UEFA Champions League spot when they face Groningen on Sunday.
He said: "After the match it will undoubtedly be emotional. But until then only the result counts.
"PSV must win to finish second and get into the Champions League. That's what I'm fighting for."