The game was drifting along without incident before exploding into life just before the break.
Two goals in as many minutes from Matt Clarke and Ben Close gave Pompey a commanding lead over Gillingham in the Checkatrade Trophy.
And a 4-0 group stage victory was completed after the break by Brett Pitman’s penalty and a late David Wheeler strike.
Kenny Jackett admitted that it took some time to get into gear, but knew that was likely after making 10 alterations to his team.
The Blues boss said: “Gillingham, like ourselves, made a number of changes and we had to wait for the game to settle.
“People had opportunities to come into the side and had to find their feet, getting their bearings off each other.
"We scored two crucial goals to put us in control at half-time and I’m pleased to say we didn’t make any mistakes after the break."
“It took us a while to get going and we didn’t really have any cohesion in the early stages, but as the game wore on, Close and Rose got into it and helped us build.
“We scored two crucial goals to put us in control at half-time and I’m pleased to say we didn’t make any mistakes after the break.
“You need your defenders to come up and get goals if you want to be successful, so it was pleasing to see Matt do that.
“To have four different scorers is a positive and they were of a different variety as well, with two from set-pieces.”
The result moves Pompey closer to a spot in the knockout stages, although Jackett currently has other priorities.
He said: “We’re not really focusing on the competition too much, but that may change if we do well and get closer to Wembley.
“There are three home matches in a week and we’ve won the first two, so now we move on to Shrewsbury on Saturday.”