Ellis Harrison toasted his stoppage-time winner at Doncaster and admitted: I wasn't sure my header was finding the top corner.
The striker glanced home James Bolton’s cross in the 91st minute to deliver Pompey a 2-1 victory at the Keepmoat Stadium.
The Blues were put under a barrage of pressure in the first half and were fortunate to go into the interval goalless.
But it was the visitors who broke the deadlock on the hour mark, with Gareth Evans finishing off a counter-attack.
Despite Reece James equalising in the 82nd minute, Harrison – who was introduced as a half-time substitute – snatched the three points for Pompey.
The summer signing from Ipswich revealed he focused on getting decent contact on the ball to ensure his effort hit the target.
And he was delighted his header looped over Donny keeper Seny Dieng, which earned Kenny Jackett’s men their first win on the road in League One this term..
Harrison said: ‘They’re such a good team and we managed to break on them a few times.
‘Gaz got in and scored and we were disappointed to concede because they boys defended well all game.
‘But we did create some chances and luckily I sniffed one out.
‘The quality of the balls that came into the box from the wingers and full-backs are always good.
‘Maybe I should have scored before that from Gaz’s cross.
‘It was more of a glance. I just thought I needed to get any contact on it to hit the target because they go over a lot so luckily it found the top corner.
‘They go over a lot. I was peeling off thinking “please go in” because the keeper made an unbelievable save from Closey (Ben Close) before it so we deserved that one.’