Brett Pitman came off the bench to score his first goal of the season and ensure Pompey began their defence of the Leasing.com Trophy with a win against Crawley.
Both sides had chances, although it appeared as if the Fratton contest might be heading for a bonus-point penalty shoot-out.
But Pitman neatly converted a corner from the impressive Brandon Haunstrup to secure all three for the Blues.
Kenny Jackett made six changes from the side that drew with Blackpool in the league at the weekend.
Haunstrup, Paul Downing, Ben Close, John Marquis and skipper Tom Naylor all kept their place in the starting line-up.
Teenager Leon Maloney was given an opportunity to impress out wide, with Ellis Harrison also recalled to the forward line.
Summer signings James Bolton and Sean Raggett were in a defence protecting Alex Bass’ goal and Gareth Evans returned in midfield.
It was a rare outing of the 4-4-2 system for the hosts and although the first half was lacking in quality, there were opportunities at both ends.
Crawley were first to go close following a quick break and Bass had to get down well to push Mason Bloomfield’s effort around the post.
Their opponents were applying plenty of pressure and dominating possession, but failing to trouble keeper Michael Luyambula.
Paul Downing conceded a free-kick right on the edge of the box on 20 minutes, only for Jack Powell to shoot straight into the wall.
The Blues soon stormed up the other end of the pitch and following good work from Harrison and Marquis, a goal-bound Evans strike was blocked by Jamie Sendles-White.
Both sides were taking advantage of some sloppy passing to steal possession and counter, and Tarryn Allarakhia was forced to stop one attack by fouling Maloney and collecting a booking.
Harrison slipped a neat pass through to Evans on the half-hour mark, but the midfielder could not find the target from an acute angle.
There was then a break in play while Evans got treatment following a challenge with Sendles-White that resulted in a yellow card for the Red Devils defender.
Both sides came close to breaking the deadlock in a breathless conclusion to the opening period of the contest.
Evans whipped in a dangerous cross that was not at the ideal height for Maloney, but he managed to fire in a shot that was saved by Luyambula.
George Francomb then fizzed an effort narrowly over the bar from the edge of the box, before Ashley Nathaniel-George sent an attempt just past the post.
Crawley Town 0
Evans – who had taken a knock on the head earlier in the game – did not emerge for the second half, with Pitman replacing him.
A couple of Haunstrup corners might have caused Crawley problems just after the restart, but his team-mates were unable to take advantage.
The visitors then had a chance to score when the ball was cut back for unmarked substitute Nathan Ferguson in the box, with Bolton making a timely block.
Bass soon had to tear from his line to beat Ashley Nadesan to the ball, with the Red Devils man needing treatment after the pair collided.
Naylor played a clever pass over the defence for the onside Harrison to collect just past the hour mark, although his cut-back for Marquis was intercepted.
Then, after a quickly-taken free-kick broke down, Bolton claimed possession, cut on to his left foot and curled narrowly wide.
It looked like the opening goal would arrive on 68 minutes after Haunstrup had delivered a superb cross, but Luyambula pulled off a fine save to keep out Harrison’s header from point-blank range.
Maloney then sent in a dangerous ball of his own that was nodded back by Marquis and hacked over the bar by Sendles-White.
And it was from the resulting corner that the hosts took the lead, with another excellent Haunstrup cross hooked home by PITMAN.
The left-back’s delivery had been a particular highlight and a low centre was then met by Pitman again, although this time Crawley were able to block.
Pompey then saw out the final stages in relatively comfortable fashion to get the group stage campaign off to a successful start.
Pompey (4-4-2): Bass; Bolton, Downing, Raggett, Haunstrup; Maloney, Naylor (c), Close, Evans (Pitman 46); Harrison, Marquis
Goals: Pitman 70
Subs not used: McGee, Casey, Burgess, Hancott, Walkes, Flint
Crawley (4-1-4-1): Luyambula; Francomb, Sendles-White, Dallison (Tunnicliffe 46), Young (c); Payne; Nadesan, Powell (Ferguson 54), Allarakhia (Galach 80), Nathaniel-George; Bloomfield
Booked: Allarakhia, Sendles-White
Subs not used: Morris, Forrest, Doherty, Camara
Referee: James Linington
Attendance: 3,784 (96 away fans)