Pompey's 100% record in League One continued tonight as goals from Gareth Evans and Ronan Curtis earned a hard fought 2-1 win at the Memorial Stadium.
Kenny Jackett's men started the game on the front foot and dominated possession early on but the Gas played their way into the game and Liam Sercombe wasted a great chance to put the hosts ahead when he was found inside the box but could only skew his shot wide.
Just as Rovers took control of the game, Pompey gained the lead as Craig MacGillivray's long punt upfield was helped on by Oli Hawkins and Curtis before Evans volleyed the ball into the roof of the net.
The remainder of the half was a fairly even affair with both sides combative in midfield and looking dangerous when going forward but MacGillivray only had one save to make when he pushed away Sercombe's effort from the edge of the box.
Pompey began the second half brightly but soon found themselves under the cosh and unable to keep the ball as the Gas upped the pressure with just a single wide attempt from Evans the only real respite.
The home crowd had been optimistically shouting for handball during the second half and they got their wish when Curtis was somewhat harshly penalised for a deliberate handball in the box.
Substitute Chris Lines just about squeezed the ball past MacGillivray into the corner for the equaliser but he wouldn't last much longer on the pitch as he was shown a straight red card for a nasty challenge on Brett Pitman.
With ten men, it seemed Rovers were happy with a point as goalkeeper Adam Smith took an age to take his goal kicks. Jamal Lowe was then on the receiving end of abuse from Pitman as his shot from an angle hit the side netting when he could have squared the ball, whilst Alex Jakubiak forced MacGillivray to palm a shot away.
The tenacity from Pompey finally paid dividends in the 87th minute when Pitman's flick on reached Curtis and his effort struck the hand of Smith before just about crossing the goal line.
There was time for more drama as Kyle Bennett almost equalised against his former club only for MacGillivray to deny him with a superb save at close range. The resulting corner then saw Pitman clear the ball off the line and the visitors were able to see out the six minutes of stoppage time and claim an impressive victory.
To come out of that match with all three points is Pompey's best result of the season so far as they really had to dig in during the second half. MacGillivray, Matt Clarke and Jack Whatmough were superb at the heart of the defence and the midfield did a solid job in winning tackles in the centre of the pitch but struggled to play a decent pass forward into feet.
It has to be said that although Hawkins worked hard and played his part in the goal, he didn't do a very good job at holding the ball up and it could be argued that Pitman had more of an impact than him in the match despite only playing 19 minutes of the game.
However, this is a team built on grit and a solid defensive foundation that might not have too much guile ot the ability to play tippy-tappy football, but every player gives everything and from the frontmen who are a nuisance to play against to the stalwerts at the back, Kenny Jackett has the makings of a successful squad.
The last time Pompey won their four opening league games of the season was all the way back in 1980 yet in 2018 they still share their 100% record with Peterborough whose late penalty at The Valley ensured they also won their fourth game in four.
Can the Blues make it a perfect August with a fifth straight win on Saturday when they take on Doncaster?
Pompey Player Ratings
Craig MacGillivray: 9 - Some superb saves to ensure Pompey preserved their lead.
Anton Walkes: 7 - Did more than a solid job.
Matt Clarke: 8 - Showed his quality with the ball at his feet as well as his aerial prowess.
Jack Whatmough: 8 - Another accomplished display for the most part.
Lee Brown: 7 - Decent return to his old ground.
Tom Naylor: 7 - Won more than his fair share of challenges.
Ben Thompson: 7 - Put himself about despite a couple of poor passes.
Gareth Evans: 8 - The driving force in the Pompey side.
Jamal Lowe: 6 - Got himself in behind a few times but nothing came off for him.
Ronan Curtis: 7 - Full of running and bagged the winner despite giving away earlier penalty.
Oli Hawkins: 6 - Struggled against Lockyer when trying to win/keep the ball.
Brandan Haunstrup (Curtis 90): N/A - Late defensive switch.
Brett Pitman (Hawkins 77): N/A - Made an important difference both going forward and at the back.