Steve Cotterill admitted: We got what we deserved.
The Blues boss confessed his side turned in their worst home performance of the season as they fell to a 2-1 defeat against Burnley.
Burnley got just their second away win of the campaign and third victory in 35 on their travels.
Pompey deserved nothing from the game as they failed to carve out little of note after John Utaka cancelled out Jay Rodriguez's opener.
Dean Marney got the decisive goal eight minutes before the break.
Cotterill said: 'We got what we deseved. It was our worst home performance of the season.
'I can't put my finger on what went wrong.
'We weren't good enough and full credit to Burnley.'
Cotterill felt Jonathan Hogg delivered a reasonable performance on his first start following his loan signing from Aston Villa.
He said: 'Hogg did okay, but it was difficult for him after just arriving.'