Pompey are basking in a 3-1 victory at Rochdale that saw them restored to the League One summit.
But such an outcome did not look certain when they fell behind less than four minutes into the Spotland contest.
A sumptuous long-range strike from Aaron Wilbraham saw the hosts forge ahead and left the travelling fans stunned.
They need not have worried, however, as goals from Jamal Lowe, Brett Pitman and Matt Clarke secured the points.
And Joe Gallen was delighted that the Blues did not show an adverse reaction to conceding so early in the game.
Pompey’s assistant manager said: “We’re in a results business and to collect three points away from home is certainly pleasing.
“You always get a tough game up here and I remember it was toing and froing when we played Rochdale last season.
"We might have wobbled a bit at that point, but we didn’t and instead came back strongly to dominate the first half."
“So it’s great that we’ve been able to extend our unbeaten run and it was a good reaction to falling behind.
“We might have wobbled a bit at that point, but we didn’t and instead came back strongly to dominate the first half. We were unlucky not to be winning at half-time.
“It’s going to give us confidence and being top of the table is nice, although it doesn’t really mean anything at this stage.”
Pitman has largely been used as a substitute this season, but was preferred to Oli Hawkins against Rochdale and produced a fine all-round performance.
Gallen said: “There’s a fight going on for the number nine shirt – and I include Joe Mason in that as well.
“Oli’s had it because of the recent results and the way things have been going, but Brett’s been putting him under pressure.
“Now he’s got the shirt and I’m sure it will be Oli and Joe that are applying the pressure going forward.
“That’s exactly what you want from your squad and it helps to build a winning mentality that we’re all looking for.
“There were other players who were substitutes – and some who weren’t in the squad at all – and they’re all capable.”