Stephen Henderson admitted his elevation to Pompey No1 came out of the blue.
The Irish keeper made his Blues league debut at Leeds on Saturday after replacing Jamie Ashdown.
Ashdown was dropped after a rare off day against Peterborough last week.
Henderson delivered a competent display at Elland Road in his place.
The 23-year-old made a couple of decent stops and couldn’t be faulted for the goal Pompey conceded.
He explained he didn’t find out he was starting until Saturday morning – and the news came as something of a shock.
Henderson said: ‘It was great to start.
‘I’ve been playing second to Jamie at the moment.
‘So it was good to start but I’m just annoyed at the result because 700 fans have travelled to watch us. I wanted to send them back with something.
‘It was a bit out of the blue – Jamie has done really well.
‘I’ve been working hard in training.
‘I got the call on Saturday morning and I was ready for it.
‘The manager just dragged me to one side on the morning and told me I was playing.
‘I just tried to act as I normally would.
‘It was a bonus to play and I really enjoyed it, apart from the result.’
Henderson, like most of the Pompey squad, was at a loss to explain Pompey’s Jekyll & Hyde display.
The Blues were woeful in the first-half and dominant after the break.
Henderson felt his side were unfortunate not to turn their pressure into goals.
But he knows they can ill afford to start so poorly against any of their rivals.
Henderson said: ‘It was devastating to lose.
‘In the second-half we were just a different team.
‘We had so many chances but the luck just wouldn’t run for us.
‘The lads are disappointed but we have a week to refresh now over the international break and we have to come back flying.
‘The lads have said a lot things after the game.
‘We started off too slowly.
‘You can’t come to a place like Leeds and start how we did.
‘We need to play how we did in the second half for the whole game.’