Confidence was high as Pompey made the trip to Oakwell on the back of three successive League One victories.
But an in-form Barnsley side brought them back down to earth by recording a 3-1 victory to continue their promotion push.
Colby Bishop had nodded the visitors back into the contest following goals from James Norwood and Nicky Cadden, only for Devante Cole to extinguish any hopes of a comeback.
John Mousinho accepted that the Tykes were ultimately deserving of all three points and knows his side have room for improvement.
The Blues boss said: “The result was probably about right in terms of what we deserved and it’s a difficult one to pick the bones out of straight after the game.
“Off the back of the highs of last week, we weren’t able to replicate those levels against one of the division’s better sides. It’s probably a good indication of where we are.
“The mistake that led to us falling behind is one of those unfortunate things and we’re asking the boys to be brave on the ball, so I accept that.
"Off the back of the highs of last week, we weren’t able to replicate those levels against one of the division’s better sides. It’s probably a good indication of where we are."
“But we let ourselves down collectively by not reacting well and after a fairly placid first 15 minutes, Barnsley were on top of us.
“We suddenly found ourselves two down and when you’re away from home, it’s going to be difficult to get back in the game.
“The message at the break was to make sure that we stayed in it and the momentum immediately shifted.
“We knew one goal could change the fabric of the match and that’s what happened for a bit, but conceding again just took the sting out of things.
“The longer we could keep it at 2-1, then the more nervous Barnsley become and the more nervous the ground becomes.
“People were talking about this being a make or break fixture, but there are still plenty of points to play for and we’ll dust ourselves down ahead of Saturday.”
One positive for the healthy travelling contingent was seeing Tom Lowery make his first start since mid-September.
Mousinho said: “It was a tough one to chuck him back into, but he’d done well at the weekend and it’s brilliant to see him back in the fold.”