Steve Cotterill revealed his frustrations after a forgettable draw with Middlesbrough.
The Fratton Park clash with the Championship strugglers finished goalless.
And the Blues boss was at a loss to put his finger on the reason behind it.
He said: ‘It just didn’t get going out there, We were just waiting for it to change.
‘It was real stop-start, all the time. It just never flowed.
‘The was down to the referee.
‘I thought we looked tired out there at times after so many games recently.
‘It just wasn’t happening.’