Paul Downing admitted that it was a disappointing way to make his competitive Pompey debut.
The summer signing produced a solid performance at the back, but it was not enough to prevent a 1-0 defeat at Shrewsbury.
A fine long-range strike from Ryan Giles settled a contest in which the Blues controlled possession and had Ross McCrorie sent off.
Downing knows that the visitors did not make the most of their dominance, but is confident they can soon build a winning mentality.
The centre-back said: “We were frustrated in the dressing room – especially regarding our end product.
“There were plenty of times when we got into good positions, but didn’t test their keeper enough and wasted opportunities.
“It is still very early days, though, so we can’t be too down about it and have to pick ourselves back up quickly.
“We restricted Shrewsbury to very little and looked really solid, with some strong foundations – it took a wonder strike for them to score.
"It is still very early days, though, so we can’t be too down about it and have to pick ourselves back up quickly."
“Those relationships are starting to develop all over the pitch and we need to take that on to the next game.
“We kept going, even after being reduced to 10 men, and that’s something we need to keep going forwards.
“There are obviously a few new faces in the squad, so you do need a bit of time for everyone to bed in.
“We’re certainly not going to get carried away about losing the first game and we want to get off the mark against Tranmere.
“You definitely feel the frustration because we wanted to start positively, so hopefully the fans will stay patient and there’s enough experience for us to bounce back.”