Those fans who travelled to Roots Hall would have been encouraged when Conor Chaplin went close to scoring in the opening seconds.
But their hopes were soon dashed, as Pompey instead found themselves two goals down after 12 minutes.
Matt Clarke’s unfortunate own-goal and a Jason Demetriou strike for Southend left the visitors stunned.
Gareth Evans did reduce the deficit, although Nathan Thompson’s red card and a second Demetriou effort ensured there was no comeback.
And Kenny Jackett is frustrated that sloppy defending has cost Pompey plenty of points since the turn of the year.
The Blues boss said: “It’s too many games for us now without a clean sheet and we’ve conceded three times on this occasion.
"It was very brittle for us defensively – and that’s been the case throughout January and February."
“We started well and Conor had the first chance, but they then got into our half twice and we gifted Southend two goals.
“It was very brittle for us defensively – and that’s been the case throughout January and February. It has to improve.
“We have to gives ourselves a basis to build on. If your goals against column is zeroes and ones then you give yourselves a chance.
“But we’re giving them away at the moment, which is frustrating and it’s undermining our confidence.
“It leaves a mountain for us to climb and this game was only a reflection of what we’ve seen over the past couple of months.
“There aren’t fantastic pieces of skill needed to score against us. They’re easy and avoidable goals, and it’s costing us.”
Thompson was dismissed for a challenge on Shrimpers skipper Ben Coker just past the hour mark and will now serve a three-match ban.
Jackett sad: “It was slightly high and so it didn’t surprise me when the referee showed the red card.
“There will now be opportunities for other players and we had to substitute Pitman and Evans. We’ll see whether they can make Tuesday or not.”