Jamal Lowe believes Pompey were left with too much to do after a disastrous start at Southend.
A showcase of sloppy defending led to the Blues conceding twice inside the opening 12 minutes at Roots Hall.
Gareth Evans pulled one back before the break, only for Nathan Thompson to be sent off for a late challenge.
And Lowe was disappointed that Pompey were unable to stage a comeback before the Shrimpers added a third goal late on.
The winger said: “As you can imagine, we were all extremely disappointed after the final whistle.
“To concede two goals so early on left us with a mountain to climb, but we almost managed to do that.
“It gives the opposition some confidence and knocks ours down a bit because you know there’s a lot to do.
"To concede two goals so early on left us with a mountain to climb."
“We had to come out strongly at the start of the second half and even after Tommo was sent off, I felt we were in control.
“They weren’t really doing much with their possession and we were able to create a few chances that we couldn’t take.
“I think we just left it a bit too late to make that push and the third from Southend wrapped things up.
“They were doing everything they could from that point to drag the game out, which is what you do in that position.
“Now the whole squad has to come together because every member has something to prove and we need to pick things up.”
It was a difficult day all round for Pompey, with injuries to Evans and Brett Pitman adding to Thompson’s dismissal.
Lowe said: “It was just one thing after another for us. You want to stay with 11 men and you want your top scorer on the pitch.
“Gaz is one of our best crossers of the ball, so it was tough for us to take with everything that went on.”