Pompey’s League One promotion hopes suffered a setback at Bristol Rovers.
John Marquis’ first half opener ultimately counted for nothing, as the hosts fought back to secure a 3-1 victory.
It meant that the Blues failed to make the most of their opportunity to close the gap on the top two sides.
Rasmus Nicolaisen was one of three players brought on before the second half started at the Memorial Stadium.
And he admitted that Pompey ultimately got what they deserved for an unusually poor away performance.
The Danish centre-back said: “We didn’t play our own game and instead got into playing it how they wanted.
"Teams at the top of the table can’t have results like that. You need to be sharp – a lot sharper than we were."
“It felt in the first half like they just wanted it more than us and that’s obviously not how it should be.
“But it isn’t really like us to make those mistakes. There have been so many games when we’ve been good and shown character.
“Teams at the top of the table can’t have results like that. You need to be sharp – a lot sharper than we were.
“Maybe we should have played it more simple, got the ball down the side and put in crosses, which is where we’re usually dangerous.
“It wasn’t an easy pitch to play on, so we needed to be clever and be simple. But we made it too hard for ourselves.
“I’m sure we’ll be able to bounce back, though. It’s important that we put this result right at the weekend.”